Semi-solid electrodes having high rate capability

ABSTRACT

Embodiments described herein relate generally to electrochemical cells having high rate capability, and more particularly to devices, systems and methods of producing high capacity and high rate capability batteries having relatively thick semi-solid electrodes. In some embodiments, an electrochemical cell includes an anode and a semi-solid cathode. The semi-solid cathode includes a suspension of an active material of about 35% to about 75% by volume of an active material and about 0.5% to about 8% by volume of a conductive material in a non-aqueous liquid electrolyte. An ion-permeable membrane is disposed between the anode and the semi-solid cathode. The semi-solid cathode has a thickness of about 250 μm to about 2,000 μm, and the electrochemical cell has an area specific capacity of at least about 7 mAh/cm 2  at a C-rate of C/4. In some embodiments, the semi-solid cathode slurry has a mixing index of at least about 0.9.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/792,179, filed Oct. 24, 2017, entitled “Semi-Solid Electrodes HavingHigh Rate Capability,” which is a continuation of U.S. patentapplication Ser. No. 15/148,048, filed May 6, 2016, entitled “Semi-SolidElectrodes Having High Rate Capability,” now U.S. Pat. No. 9,831,518,which is a continuation of U.S. patent application Ser. No. 14/719,566,filed May 22, 2015, now U.S. Pat. No. 9,362,583, entitled “Semi-SolidElectrodes Having High Rate Capability,” which is a continuation ofinternational patent application PCT/US2013/075106, filed Dec. 13, 2013,entitled “Semi-Solid Electrodes Having High Rate Capability,” which is acontinuation-in-part of and claims priority to U.S. patent applicationSer. No. 13/872,613, filed Apr. 29, 2013, now U.S. Pat. No. 8,993,159,entitled “Semi-Solid Electrodes Having High Rate Capability,” whichclaims priority to and the benefit of U.S. Provisional Application No.61/736,798, filed Dec. 13, 2012, “Electrochemical Slurry CompositionsHaving High Rate Capability,” and U.S. Provisional Application No.61/787,382, filed Mar. 15, 2013, “Semi-Solid Electrodes Having High RateCapability,” the disclosures of each of which are hereby incorporated byreference in their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Grant NumberDE-AR0000102 awarded by the Department of Energy. The government hascertain rights in the invention.

BACKGROUND

Embodiments described herein relate generally to electrochemical cellshaving high rate capability, and more particularly to devices, systemsand methods of producing high capacity and high rate capabilitybatteries having relatively thick semi-solid electrodes.

Batteries are typically constructed of solid electrodes, separators,electrolyte, and ancillary components such as, for example, packaging,thermal management, cell balancing, consolidation of electrical currentcarriers into terminals, and/or other such components. The electrodestypically include active materials, conductive materials, binders andother additives.

Some known methods for preparing batteries include coating a metallicsubstrate (e.g., a current collector) with slurry composed of an activematerial, a conductive additive, and a binding agent dissolved ordispersed in a solvent, evaporating the solvent, and calendering thedried solid matrix to a specified thickness. The electrodes are thencut, packaged with other components, infiltrated with electrolyte andthe entire package is then sealed.

Such known methods generally involve complicated and expensivemanufacturing steps such as casting the electrode and are only suitablefor electrodes of limited thickness, for example, less than 100 μm(final single sided coated thickness). These known methods for producingelectrodes of limited thickness result in batteries with lower capacity,lower energy density and a high ratio of inactive components to activematerials. Furthermore, the binders used in known electrode formulationscan increase tortuosity and decrease the ionic conductivity of theelectrode.

Thus, it is an enduring goal of energy storage systems development tosimplify and reduce manufacturing cost, reduce inactive components inthe electrodes and finished batteries, and increase energy density,charge capacity and overall performance.

SUMMARY

Embodiments described herein relate generally to electrochemical cellshaving high rate capability, and more particularly to devices, systemsand methods of producing high capacity and high rate capabilitybatteries having relatively thick semi-solid electrodes. In someembodiments, an electrochemical cell includes an anode and a semi-solidcathode. The semi-solid cathode includes a suspension of about 35% toabout 75% by volume of an active material and about 0.5% to about 8% byvolume of a conductive material in a non-aqueous liquid electrolyte. Anion permeable membrane disposed between the anode and the cathode. Thesemi-solid cathode has a thickness in the range of about 250 μm-2,500μm, and the electrochemical cell has an area specific capacity of atleast 7 mAh/cm² at a C-rate of C/4. In some embodiments, the semi-solidcathode slurry has a mixing index of at least about 0.9.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an electrochemical cell accordingto an embodiment.

FIGS. 2A-2C and FIGS. 3A-3C are schematic illustrations of semi-solidsuspensions, according to various embodiments.

FIG. 4 is a plot of the conductivity of a semi-solid electrode versusconductive additive loading, according to various embodiments.

FIGS. 5A-5C depict electrode slurry mixtures with different conductiveadditive loadings, according to various embodiments.

FIGS. 6-9 are plots illustrating rheological characteristics of slurryformulations, according to various embodiments.

FIGS. 10-12 are plots illustrating mixing curves, according to variousembodiments.

FIG. 13 is a plot illustrating the relationship of mixing index withspecific energy input and conductive additive loading, according tovarious embodiments.

FIG. 14 is a plot illustrating the effect of mixing on certain slurryparameters, according to various embodiments.

FIG. 15 illustrates the evolution of mixing index and conductivity withmixing duration at 100 rpm, for two different cathode compositions.

FIG. 16 illustrates the evolution of mixing index and conductivity withmixing duration at 100 rpm, for two different anode compositions.

FIG. 17 is a plot illustrating conductivity as a function of mixing timefor two shear conditions, according to various embodiments.

FIG. 18 illustrates the mixing index over time for two differentexemplary cathode compositions.

FIG. 19 illustrates the mixing index over time for two differentexemplary anode compositions.

FIG. 20 illustrates the area specific capacity vs. current density atvarious C-rates of seven different electrochemical cells that include atleast one semi-solid electrode described herein, in comparison withcommercially available batteries.

DETAILED DESCRIPTION

Consumer electronic batteries have gradually increased in energy densitywith the progress of lithium-ion battery technology. The stored energyor charge capacity of a manufactured battery is a function of: (1) theinherent charge capacity of the active material (mAh/g), (2) the volumeof the electrodes (cm³) (i.e., the product of the electrode thickness,electrode area, and number of layers (stacks)), and (3) the loading ofactive material in the electrode media (e.g., grams of active materialper cm³ of electrode media). Therefore, to enhance commercial appeal(e.g., increased energy density and decreased cost), it is generallydesirable to increase the areal charge capacity (mAh/cm²) also referredto as “area specific capacity” or “area capacity” herein. The arealcharge capacity can be increased, for example, by utilizing activematerials that have a higher inherent charge capacity, increasingrelative percentage of active charge storing material (i.e., “loading”)in the overall electrode formulation, and/or increasing the relativepercentage of electrode material used in any given battery form factor.Said another way, increasing the ratio of active charge storingcomponents (e.g., the electrodes) to inactive components (e.g., theseparators and current collectors), increases the overall energy densityof the battery by eliminating or reducing components that are notcontributing to the overall performance of the battery. One way toaccomplish increasing the areal charge capacity, and therefore reducingthe relative percentage of inactive components, is by increasing thethickness of the electrodes.

Conventional electrode compositions have capacities of approximately150-200 mAh/g and generally cannot be made thicker than about 100 μmbecause of certain performance and manufacturing limitations. Forexample, i) conventional electrodes having a thickness over 100 μm(single sided coated thickness) typically have significant reductions intheir rate capability due to diffusion limitations through the thicknessof the electrode (e.g. porosity, tortuosity, impedance, etc.) whichgrows rapidly with increasing thickness; ii) thick conventionalelectrodes are difficult to manufacture due to drying and postprocessing limitations, for example, solvent removal rate, capillaryforces during drying that leads to cracking of the electrode, pooradhesion of the electrode to the current collector leading todelamination (e.g., during the high speed roll-to-roll calenderingprocess used for manufacturing conventional electrodes), migration ofbinder during the solvent removal process and/or deformation during asubsequent compression process; iii) without being bound to anyparticular theory, the binders used in conventional electrodes mayobstruct the pore structure of the electrodes and increase theresistance to diffusion of ions by reducing the available volume ofpores and increasing tortuosity (i.e. effective path length) byoccupying a significant fraction of the space between the functionalcomponents of the electrodes (i.e. active and conductive components). Itis also known that binders used in conventional electrodes can at leastpartially coat the surface of the electrode active materials, whichslows down or completely blocks the flow of ions to the activematerials, thereby increasing tortuosity.

Furthermore, known conventional batteries either have high capacity orhigh rate capability, but not both. A battery having a first chargecapacity at first C-rate, for example, 0.5 C generally has a secondlower charge capacity when discharged at a second higher C-rate, forexample, 2 C. This is due to the higher energy loss that occurs inside aconventional battery due to the high internal resistance of conventionalelectrodes (e.g. solid electrodes with binders), and a drop in voltagethat causes the battery to reach the low-end voltage cut-off sooner. Thetheoretical area specific capacity can hypothetically be increasedwithout limit by increasing the thickness of the electrode and/or byincreasing the volume fraction of the active material in the electrode.However, such arbitrary increases in theoretical area specific capacityare not useful if the capacity cannot be used at a practical C-rate.Increases in area specific capacity that cannot be accessed at practicalC-rates are highly detrimental to battery performance. The capacityappears as unused mass and volume rather than contributing to storedenergy, thereby lowering the energy density and area specific capacityof the battery. Moreover, a thicker electrode generally has a higherinternal resistance and therefore a lower rate capability. For example,a lead acid battery does not perform well at 1 C C-rate. They are oftenrated at a 0.2 C C-rate and even at this low C-rate, they cannot attain100% capacity. In contrast, ultracapacitors can be discharged at anextremely high C-rate and still maintain 100% capacity, however, theyhave a much lower capacity than conventional batteries. Accordingly, aneed exists for batteries with thicker electrodes, but without theaforementioned limitations. The resulting batteries with superiorperformance characteristics, for example, superior rate capability andcharge capacity, and also are simpler to manufacture.

Semi-solid electrodes described herein can be made: (i) thicker (e.g.,greater than about 250 μm—up to about 2,000 μm or even greater) due tothe reduced tortuosity and higher electronic conductivity of thesemi-solid electrode, (ii) with higher loadings of active materials,(iii) with a simplified manufacturing process utilizing less equipment,and (iv) can be operated between a wide range of C-rates whilemaintaining a substantial portion of its theoretical charge capacity.These relatively thick semi-solid electrodes decrease the volume, massand cost contributions of inactive components with respect to activecomponents, thereby enhancing the commercial appeal of batteries madewith the semi-solid electrodes. In some embodiments, the semi-solidelectrodes described herein are binderless and/or do not use bindersthat are used in conventional battery manufacturing. Instead, the volumeof the electrode normally occupied by binders in conventionalelectrodes, is now occupied by: 1) electrolyte, which has the effect ofdecreasing tortuosity and increasing the total salt available for iondiffusion, thereby countering the salt depletion effects typical ofthick conventional electrodes when used at high rate, 2) activematerial, which has the effect of increasing the charge capacity of thebattery, or 3) conductive additive, which has the effect of increasingthe electronic conductivity of the electrode, thereby countering thehigh internal impedance of thick conventional electrodes. The reducedtortuosity and a higher electronic conductivity of the semi-solidelectrodes described herein, results in superior rate capability andcharge capacity of electrochemical cells formed from the semi-solidelectrodes. Since the semi-solid electrodes described herein, can bemade substantially thicker than conventional electrodes, the ratio ofactive materials (i.e., the semi-solid cathode and/or anode) to inactivematerials (i.e. the current collector and separator) can be much higherin a battery formed from electrochemical cell stacks that includesemi-solid electrodes relative to a similar battery formed formelectrochemical cell stacks that include conventional electrodes. Thissubstantially increases the overall charge capacity and energy densityof a battery that includes the semi-solid electrodes described herein.

In some embodiments, an electrochemical cell includes an anode, and asemi-solid cathode. The semi-solid cathode includes a suspension ofabout 35% to about 75% by volume of an active material and about 0.5% toabout 8% by volume of a conductive material in a non-aqueous liquidelectrolyte. An ion-permeable membrane is disposed between the anode andthe semi-solid cathode. The semi-solid cathode has a thickness in therange of about 250 μm to about 2,000 μm and the electrochemical cell hasan area specific capacity of at least about 7 mAh/cm² at a C-rate ofC/4. In some embodiments, the semi-solid cathode suspension has anelectronic conductivity of at least about 10⁻³ S/cm. In someembodiments, the semi-solid cathode suspension has a mixing index of atleast about 0.9.

In some embodiments, an electrochemical cell includes a semi-solid anodeand a semi-solid cathode. The semi-solid anode includes a suspension ofabout 35% to about 75% by volume of a first active material and about 0%to about 10% by volume of a first conductive material in a firstnon-aqueous liquid electrolyte. The semi-solid cathode includes asuspension of about 35% to about 75% by volume of a second activematerial, and about 0.5% to about 8% by volume of a second conductivematerial in a second non-aqueous liquid electrolyte. An ion-permeablemembrane is disposed between the semi-solid anode and the semi-solidcathode. Each of the semi-solid anode and the semi-solid cathode have athickness of about 250 μm to about 2,000 μm and the electrochemical cellhas an area specific capacity of at least about 7 mAh/cm² at a C-rate ofC/4. In some embodiments, the first conductive material included in thesemi-solid anode is about 0.5% to about 2% by volume. In someembodiments, the second active material included in the semi-solidcathode is about 50% to about 75% by volume.

In some embodiments, an electrochemical cell includes an anode and asemi-solid cathode. The semi-solid cathode includes a suspension ofabout 35% to about 75% by volume of an active material and about 0.5% toabout 8% by volume of a conductive material in a non-aqueous liquidelectrolyte. An ion-permeable membrane is disposed between the anode andsemi-solid cathode. The semi-solid cathode has a thickness in the rangeof about 250 μm to about 2,000 μm, and the electrochemical cell has anarea specific capacity of at least about 7 mAh/cm² at a C-rate of C/2.In some embodiments, the semi-solid cathode suspension has a mixingindex of at least about 0.9.

In some embodiments, an electrochemical cell includes a semi-solid anodeand a semi-solid cathode. The semi-solid anode includes a suspension ofabout 35% to about 75% by volume of a first active material and about 0%to about 10% by volume of a first conductive material in a firstnon-aqueous liquid electrolyte. The semi-solid cathode includes asuspension of about 35% to about 75% by volume of a second activematerial, and about 0.5% to about 8% by volume of a second conductivematerial in a second non-aqueous liquid electrolyte. An ion-permeablemembrane is disposed between the semi-solid anode and the semi-solidcathode. Each of the semi-solid anode and the semi-solid cathode have athickness of about 250 μm to about 2,000 μm and the electrochemical cellhas an area specific capacity of at least about 7 mAh/cm² at a C-rate ofC/2. In some embodiments, the first conductive material included in thesemi-solid anode is about 0.5% to about 2% by volume. In someembodiments, the second active material included in the semi-solidcathode is about 50% to about 75% by volume.

In some embodiments, the electrode materials described herein can be aflowable semi-solid or condensed liquid composition. A flowablesemi-solid electrode can include a suspension of an electrochemicallyactive material (anodic or cathodic particles or particulates), andoptionally an electronically conductive material (e.g., carbon) in anon-aqueous liquid electrolyte. Said another way, the active electrodeparticles and conductive particles are co-suspended in an electrolyte toproduce a semi-solid electrode. Examples of battery architecturesutilizing semi-solid suspensions are described in International PatentPublication No. WO 2012/024499, entitled “Stationary, Fluid RedoxElectrode,” and International Patent Publication No. WO 2012/088442,entitled “Semi-Solid Filled Battery and Method of Manufacture,” theentire disclosures of which are hereby incorporated by reference.

In some embodiments, semi-solid electrode compositions (also referred toherein as “semi-solid suspension” and/or “slurry”) described herein canbe mixed in a batch process e.g., with a batch mixer that can include,e.g., a high shear mixture, a planetary mixture, a centrifugal planetarymixture, a sigma mixture, a CAM mixture, and/or a roller mixture, with aspecific spatial and/or temporal ordering of component addition, asdescribed in more detail herein. In some embodiments, slurry componentscan be mixed in a continuous process (e.g. in an extruder), with aspecific spatial and/or temporal ordering of component addition.

The mixing and forming of a semi-solid electrode generally includes: (i)raw material conveyance and/or feeding, (ii) mixing, (iii) mixed slurryconveyance, (iv) dispensing and/or extruding, and (v) forming. In someembodiments, multiple steps in the process can be performed at the sametime and/or with the same piece of equipment. For example, the mixingand conveyance of the slurry can be performed at the same time with anextruder. Each step in the process can include one or more possibleembodiments. For example, each step in the process can be performedmanually or by any of a variety of process equipment. Each step can alsoinclude one or more sub-processes and, optionally, an inspection step tomonitor process quality.

In some embodiments, the process conditions can be selected to produce aprepared slurry having a mixing index of at least about 0.80, at leastabout 0.90, at least about 0.95, or at least about 0.975. In someembodiments, the process conditions can be selected to produce aprepared slurry having an electronic conductivity of at least about 10⁻⁶S/cm, at least about 10⁻⁵ S/cm, at least about 10⁴ S/cm, at least about10⁻³ S/cm, or at least about 10⁻² S/cm. In some embodiments, the processconditions can be selected to produce a prepared slurry having anapparent viscosity at room temperature of less than about 100,000 Pa·s,less than about 10,000 Pa·s, or less than about 1,000 Pa·s, all at anapparent shear rate of 1,000 s⁻¹. In some embodiments, the processconditions can be selected to produce a prepared slurry having two ormore properties as described herein. Examples of systems and methodsthat can be used for preparing the semi-solid compositions and/orelectrodes are described in U.S. patent application Ser. No. 13/832,861,filed Mar. 15, 2013, entitled “Electrochemical Slurry Compositions andMethods for Preparing the Same,” the entire disclosure of which ishereby incorporated by reference.

As used herein, the term “about” and “approximately” generally mean plusor minus 10% of the value stated, e.g., about 250 μm would include 225μm to 275 μm, about 1,000 μm would include 900 μm to 1,100 μm.

As used herein, the term “semi-solid” refers to a material that is amixture of liquid and solid phases, for example, such as particlesuspension, colloidal suspension, emulsion, gel, or micelle.

As used herein, the term “condensed ion-storing liquid” or “condensedliquid” refers to a liquid that is not merely a solvent, as in the caseof an aqueous flow cell semi-solid cathode or anode, but rather, it isitself redox active. Of course, such a liquid form may also be dilutedby or mixed with another, non-redox active liquid that is a diluent orsolvent, including mixing with such a diluent to form a lower-meltingliquid phase, emulsion or micelles including the ion-storing liquid.

As used herein, the terms “activated carbon network” and “networkedcarbon” relate to a general qualitative state of an electrode. Forexample, an electrode with an activated carbon network (or networkedcarbon) is such that the carbon particles within the electrode assume anindividual particle morphology and arrangement with respect to eachother that facilitates electrical contact and electrical conductivitybetween particles and through the thickness and length of the electrode.Conversely, the terms “unactivated carbon network” and “unnetworkedcarbon” relate to an electrode wherein the carbon particles either existas individual particle islands or multi-particle agglomerate islandsthat may not be sufficiently connected to provide adequate electricalconduction through the electrode.

As used herein, the term “area specific capacity”, “area capacity”, or“areal capacity” are used interchangeably to define the charge capacityof an electrode or an electrochemical cell per unit area having units ofmAh/cm².

In some embodiments, an electrochemical cell for storing energy includesan anode, a semi-solid cathode including a suspension of an activematerial and a conductive material in a non-aqueous liquid electrolyte,and an ion permeable separator disposed between the anode and thecathode. The semi-solid cathode can have a thickness in the range ofabout 250 μm to about 2,000 μm. In some embodiments, the electrochemicalcell is configured such that at a C-rate of C/4, the electrochemicalcell has an area specific capacity of at least about 7 mAh/cm², at leastabout 8 mAh/cm², at least about 9 mAh/cm², or at least about 10 mAh/cm².In some embodiments, at a C-rate of C/2, the electrochemical cell has anarea specific capacity of at least about 7 mAh/cm², at least about 8mAh/cm², or at least about 9 mAh/cm². In some embodiments, at a C-rateof 1 C, the electrochemical cell has an area specific capacity of atleast about 4 mAh/cm², at least about 5 mAh/cm², at least about 6mAh/cm², or at least about 7 mAh/cm². In some embodiments, at a C-rateof 2 C, the electrochemical cell has an area specific capacity of atleast about 3 mAh/cm², at least about 4 mAh/cm², or at least about 5mAh/cm². In some embodiments, at C-rates between about 2 C and about 5C, the electrochemical cell has an area specific capacity of at leastabout 1 mAh/cm², or at least about 2 mAh/cm².

In some embodiments, the thickness of the semi-solid cathode is at leastabout 250 μm. In some embodiments, the thickness of the semi-solidelectrodes can be at least about 300 μm, at least about 350 μm, at leastabout 400 μm, at least about 450 μm, at least about 500 μm, at leastabout 600 μm, at least about 700 μm, at least about 800 μm, at leastabout 900 μm, at least about 1,000 μm, at least about 1,500 μm, and upto about 2,000 μm, inclusive of all thicknesses therebetween.

In some embodiments, the anode can be a conventional anode, for example,a lithium metal anode or a calendered anode. In some embodiments, theanode can be a semi-solid anode that can have a thickness that issubstantially similar to the thickness of the semi-solid cathode suchas, for example, of at least about 250 μm, at least about 300 μm, atleast about 350 μm, at least about 400 μm, at least about 450 μm, atleast about 500 μm, and so on.

In some embodiments, the thickness of the semi-solid electrodes can bein the range of about 250 μm to about 2,000 μm, about 300 μm to about2,000 μm, about 350 μm to about 2,000 μm, 400 μm to about 2,000 μm,about 450 μm to about 2,000 μm, about 500 to about 2,000 μm, about 250μm to about 1,500 μm, about 300 μm to about 1,500 μm, about 350 μm toabout 1,500 μm, about 400 μm to about 1,500 μm, about 450 μm to about1,500 μm, about 500 to about 1,500 μm, about 250 μm to about 1,000 μm,about 300 μm to about 1,000 μm, about 350 μm to about 1,000 μm, about400 μm to about 1,000 μm, about 450 μm to about 1,000 μm, about 500 μmto about 1,000 μm, about 250 μm to about 750 μm, about 300 μm to about750 μm, about 350 μm to about 750 μm, about 400 μm to about 750 μm,about 450 μm to about 750 μm, about 500 μm to about 750 μm, about 250 μmto about 700 μm, about 300 μm to about 700 μm, about 350 μm to about 700μm, about 400 μm to about 700 μm, about 450 μm to about 700 μm, about500 μm to about 700 μm, about 250 μm to about 650 μm, about 300 μm toabout 650 μm, about 350 μm to about 650 μm, about 400 μm to about 650μm, about 450 μm to about 650 μm, about 500 μm to about 650 μm, about250 μm to about 600 μm, about 300 μm to about 600 μm, about 350 μm toabout 600 μm, about 400 μm to about 600 μm, about 450 μm to about 600μm, about 500 μm to about 600 μm, about 250 μm to about 550 μm, about300 μm to about 550 μm, about 350 μm to about 550 μm, about 400 μm toabout 550 μm, about 450 μm to about 550 μm, or about 500 μm to about 550μm, inclusive of all ranges or any other distance therebetween.

In some embodiments, a semi-solid anode can include an anode activematerial selected from lithium metal, carbon, lithium-intercalatedcarbon, lithium nitrides, lithium alloys and lithium alloy formingcompounds of silicon, bismuth, boron, gallium, indium, zinc, tin, tinoxide, antimony, aluminum, titanium oxide, molybdenum, germanium,manganese, niobium, vanadium, tantalum, gold, platinum, iron, copper,chromium, nickel, cobalt, zirconium, yttrium, molybdenum oxide,germanium oxide, silicon oxide, silicon carbide, any other materials oralloys thereof, and any other combination thereof.

In some embodiments, a semi-solid cathode can include about 35% to about75% by volume of an active material. In some embodiments, a semi-solidcathode can include about 40% to about 75% by volume, about 45% to about75% by volume, about 50% to about 75% by volume, about 55% to about 75%by volume, about 60% to about 75% by volume, or about 65% to about 75%by volume of an active material, inclusive of all ranges therebetween.

In some embodiments, a semi-solid cathode can include about 0.5% toabout 8% by volume of a conductive material. For example, in someembodiments, a semi-solid cathode can include about 0.6% to about 7.5%by volume, about 0.7% to about 7.0% by volume, about 0.8% to about 6.5%by volume, about 0.9% to about 6% by volume, about 1.0% to about 6% byvolume, about 1.5% to about 5.0% by volume, or about 2% to about 4% byvolume of a conductive material, inclusive of all ranges therebetween.

In some embodiments, a semi-solid cathode can include about 25% to about70% by volume of an electrolyte. In some embodiments, a semi-solidcathode can include about 30% to about 50%, or about 20% to about 40% byvolume of an electrolyte, inclusive of all ranges therebetween.

In some embodiments, a semi-solid anode can include about 35% to about75% by volume of an active material. In some embodiments, a semi-solidanode can include about 40% to about 75% by volume, about 45% to about75% by volume, about 50% to about 75% by volume, about 55% to about 75%by volume, about 60% to about 75% by volume, or about 65% to about 75%by volume of an active material, inclusive of all ranges therebetween.

In some embodiments, a semi-solid anode can include about 0% to about10% by volume of a conductive material. In some embodiments, asemi-solid anode can include about 0.2% to about 9% by volume, about0.4% to about 8% by volume, about 0.6% to about 7% by volume, about 0.8%to about 6% by volume, about 1% to about 5% by volume, or about 2% toabout 4% by volume of a conductive material, inclusive of all rangestherebetween. In some embodiments, the semi-solid anode includes about1% to about 6% by volume of a conductive material. In some embodiments,the semi-solid anode includes about 0.5% to about 2% by volume of aconductive material.

In some embodiments, a semi-solid anode can include about 10% to about70% by volume of an electrolyte. In some embodiments, a semi-solid anodecan include about 30% to about 50%, or about 20% to about 40% by volumeof an electrolyte, inclusive of all ranges therebetween.

In some embodiments, a semi-solid cathode or semi-solid anode caninclude less than about 10% by volume of a polymeric binder. In someembodiments, a semi-solid cathode or semi-solid anode can include lessthan about 5% by volume, or less than about 3% by volume, or less thanabout 1% by volume of a polymeric binder. In some embodiments, thepolymeric binder comprises polyvinylidene difluoride (PVdF).

In some embodiments, an electrochemical cell includes a semi-solidcathode that can include about 35% to about 75% by weight of an activematerial, about 0.5% to about 8% by weight of a conductive material, andabout 20% to about 40% by weight of a non-aqueous liquid electrolyte.The semi-solid cathode suspension can have mixing index of at leastabout 0.9. The semi-solid cathode can have a thickness in the range ofabout 250 μm to about 2,000 μm. The electrochemical cell also includes asemi-solid anode that can include about 35% to about 75% by weight of anactive material, about 1% to about 10% by weight of a conductivematerial, and about 20% to about 40% by weight of a non-aqueous liquidelectrolyte. The semi-solid anode suspension can have a mixing index ofat least about 0.9. The semi-solid anode can have a thickness in therange of about 250 μm to about 2,000 μm. The semi-solid anode and thesemi-solid cathode are separated by an ion permeable membrane disposedtherebetween. In such embodiments, the electrochemical cell can have anarea specific capacity of at least about 7 mAh/cm².

FIG. 1 shows a schematic illustration of an electrochemical cell 100.The electrochemical cell 100 includes a positive current collector 110,a negative current collector 120 and a separator 130 disposed betweenthe positive current collector 110 and the negative current collector120. The positive current collector 110 is spaced from the separator 130and at least partially defines a positive electroactive zone. Thenegative current collector 120 is spaced from the separator 130 and atleast partially defines a negative electroactive zone. A semi-solidcathode 140 is disposed in the positive electroactive zone and an anode150 is disposed in the negative electroactive zone. In some embodiments,the anode 150 can be a solid anode, for example, a lithium metal anode,a solid graphite electrode, or a calendered anode. In some embodiments,the anode 150 can be a semi-solid anode.

The semi-solid cathode 140 and/or anode 150 can be disposed on thepositive current collector 110 and the negative current collector 120,respectively using any suitable method, for example, coated, casted,drop coated, pressed, roll pressed, or deposited. The positive currentcollector 110 and the negative current collector 120 can be any currentcollectors that are electronically conductive and are electrochemicallyinactive under the operation conditions of the cell. Typical currentcollectors for lithium cells include copper, aluminum, or titanium forthe negative current collector and aluminum for the positive currentcollector, in the form of sheets or mesh, or any combination thereof.Current collector materials can be selected to be stable at theoperating potentials of the positive and negative electrodes of anelectrochemical cell 100. For example, in non-aqueous lithium systems,the positive current collector 110 can include aluminum, or aluminumcoated with conductive material that does not electrochemically dissolveat operating potentials of 2.5-5.0V with respect to Li/Li⁺. Suchmaterials include platinum, gold, nickel, conductive metal oxides suchas vanadium oxide, and carbon. The negative current collector 120 caninclude copper or other metals that do not form alloys or intermetalliccompounds with lithium, carbon, and/or coatings comprising suchmaterials disposed on another conductor.

The separator 130 is disposed between the semi-solid cathode 140 and theanode 150 (e.g., a semi-solid anode) can be any conventional membranethat is capable of ion transport. In some embodiments, the separator 130is a liquid impermeable membrane that permits the transport of ionstherethrough, namely a solid or gel ionic conductor. In some embodimentsthe separator 130 is a porous polymer membrane infused with a liquidelectrolyte that allows for the shuttling of ions between the cathode140 and anode 150 electroactive materials, while preventing the transferof electrons. In some embodiments, the separator 130 is a microporousmembrane that prevents particles forming the positive and negativeelectrode compositions from crossing the membrane. In some embodiments,the separator 130 is a single or multilayer microporous separator,optionally with the ability to fuse or “shut down” above a certaintemperature so that it no longer transmits working ions, of the typeused in the lithium ion battery industry and well-known to those skilledin the art. In some embodiments, the separator 130 material can includepolyethyleneoxide (PEO) polymer in which a lithium salt is complexed toprovide lithium conductivity, or Nafion™ membranes which are protonconductors. For example, PEO based electrolytes can be used as themembrane, which is pinhole-free and a solid ionic conductor, optionallystabilized with other membranes such as glass fiber separators assupporting layers. PEO can also be used as a slurry stabilizer,dispersant, etc. in the positive or negative redox compositions. PEO isstable in contact with typical alkyl carbonate-based electrolytes. Thiscan be especially useful in phosphate-based cell chemistries with cellpotential at the positive electrode that is less than about 3.6 V withrespect to Li metal. The operating temperature of the redox cell can beelevated as necessary to improve the ionic conductivity of the membrane.

The cathode 140 can be a semi-solid stationary cathode or a semi-solidflowable cathode, for example of the type used in redox flow cells. Thecathode 140 can include an active material such as a lithium bearingcompound as described in further detail below. The cathode 140 can alsoinclude a conductive material such as, for example, graphite, carbonpowder, pyrolytic carbon, carbon black, carbon fibers, carbonmicrofibers, carbon nanotubes (CNTs), single walled CNTs, multi walledCNTs, fullerene carbons including “bucky balls,” graphene sheets and/oraggregate of graphene sheets, any other conductive material, alloys orcombination thereof. The cathode 140 can also include a non-aqueousliquid electrolyte as described in further detail below.

In some embodiments, the anode 150 can be a semi-solid stationary anode.In some embodiments, the anode 150 can be a semi-solid flowable anode,for example, of the type used in redox flow cells.

The anode 150 can also include a carbonaceous material such as, forexample, graphite, carbon powder, pyrolytic carbon, carbon black, carbonfibers, carbon microfibers, carbon nanotubes (CNTs), single walled CNTs,multi walled CNTs, fullerene carbons including “bucky balls”, graphenesheets and/or aggregate of graphene sheets, any other carbonaceousmaterial or combination thereof. In some embodiments, the anode 150 canalso include a non-aqueous liquid electrolyte as described in furtherdetail herein.

In some embodiments, the semi-solid cathode 140 and/or the anode 150(e.g. a semi-solid anode) can include active materials and optionallyconductive materials in particulate form suspended in a non-aqueousliquid electrolyte. In some embodiments, the semi-solid cathode 140and/or anode 150 particles (e.g., cathodic or anodic particles) can havean effective diameter of at least about 1 μm. In some embodiments, thecathodic or anodic particles can have an effective diameter betweenabout 1 μm and about 10 μm. In other embodiments, the cathodic or anodicparticles can have an effective diameter of at least about 10 μm ormore. In some embodiments, the cathodic or anodic particles can have aneffective diameter of at less than about 1 μm. In other embodiments, thecathodic or anodic particles can have an effective diameter of at lessthan about 0.5 μm. In other embodiments, the cathodic or anodicparticles can have an effective diameter of at less than about 0.25 μm.In other embodiments, the cathodic or anodic particles can have aneffective diameter of at less than about 0.1 μm. In other embodiments,the cathodic or anodic particles can have an effective diameter of atless than about 0.05 μm. In other embodiments, the cathodic or anodicparticles can have an effective diameter of at less than about 0.01 μm.

In some embodiments, the semi-solid cathode 140 can include about 35% toabout 75% by volume of an active material. In some embodiments, thesemi-solid cathode 140 can include about 40% to about 75% by volume, 45%to about 75% by volume, about 50% to about 75% by volume, about 55% toabout 75% by volume, about 60% to about 75% by volume, or about 65% toabout 75% by volume of an active material, inclusive of all rangestherebetween.

In some embodiments, the semi-solid cathode 140 can include about 0.5%to about 8% by volume of a conductive material. In some embodiments, thesemi-solid cathode 140 can include about 0.6% to about 7.5% by volume,about 0.7% to about 7.0% by volume, about 0.8% to about 6.5% by volume,about 0.9% to about 6% by volume, about 1.0% to about 6%, about 1.5% toabout 5.0% by volume, or about 2% to about 4% by volume of a conductivematerial, inclusive of all ranges therebetween.

In some embodiments, the semi-solid cathode 140 can include about 25% toabout 70% by volume of an electrolyte. In some embodiments, thesemi-solid cathode 140 can include about 30% to about 50%, or about 20%to about 40% by volume of an electrolyte, inclusive of all rangestherebetween.

In some embodiments, the semi-solid cathode 140 can have an electronicconductivity of at least about 10⁻³ S/cm, or at least about 10⁻² S/cm.In some embodiments, the semi-solid cathode 140 suspension can have amixing index of at least about 0.9, at least about 0.95, or at leastabout 0.975.

In some embodiments, the semi-solid cathode 140 can have an areaspecific capacity of at least about 7 mAh/cm², at least about 8 mAh/cm²,at least about 9 mAh/cm², or at least about 10 mAh/cm² at a C-rate ofC/4. In some embodiments, the semi-solid cathode 140 can have an areaspecific capacity of at least about 7 mAh/cm², at least about 8 mAh/cm²,at least about 9 mAh/cm², or at least about 10 mAh/cm² at a C-rate ofC/2.

In some embodiments, the semi-solid anode 150 can include about 35% toabout 75% by volume of an active material. In some embodiments, thesemi-solid anode 150 can include about 40% to about 75% by volume, about45% to about 75% by volume, about 50% to about 75% by volume, about 55%to about 75% by volume, about 60% to about 75% by volume, or about 65%to about 75% by volume of an active material, inclusive of all rangestherebetween.

In some embodiments, the semi-solid anode 150 can include about 0% toabout 10% by volume of a conductive material. In some embodiments, thesemi-solid anode 150 can include about 0.2% to about 9% by volume, about0.4% to about 8% by volume, about 0.6% to about 7% by volume, about 0.8%to about 6% by volume, about 1% to about 5% by volume, or about 2% toabout 4% by volume of a conductive material, inclusive of all rangestherebetween.

In some embodiments, the semi-solid anode 150 can include about 1% toabout 6% by volume of a conductive material. In some embodiments, thesemi-solid anode 150 can include about 0.5% to about 2% by volume of aconductive material, inclusive of all ranges therebetween.

In some embodiments, the semi-solid anode 150 can include about 10% toabout 70% by volume of an electrolyte. In some embodiments, thesemi-solid anode 150 can include about 30% to about 50%, or about 20% toabout 40% by volume of an electrolyte, inclusive of all rangestherebetween.

In some embodiments, the semi-solid anode 150 suspension can have amixing index of at least about 0.9, at least about 0.95, or at leastabout 0.975.

In some embodiments, the semi-solid cathode 140 and/or the semi-solidanode 150 can have a thickness in the range of about 250 μm to about2,000 μm. In some embodiments, the semi-solid cathode 140 and/or thesemi-solid anode 150 can have a thickness in the range of about 250 μmto about 600 μm, about 300 μm to about 600 μm, about 350 μm to about 600μm, about 400 μm to about 600 μm, about 450 μm to about 600 μm, or about500 μm to about 600 μm, inclusive of all ranges therebetween.

In some embodiments, the electrochemical cell 100 can include thesemi-solid cathode 140 and a semi-solid anode 150. In such embodiments,the electrochemical cell 100 can have an area specific capacity of atleast about 7 mAh/cm² at a C-rate of C/4. In some embodiments, theelectrochemical cell 100 can have an area specific capacity of at leastabout 8 mAh/cm², at least about 9 mAh/cm², or at least about 10 mAh/cm²at a C-rate of C/4. In some embodiments, the electrochemical cell 100can have an area specific capacity of at least about 7 mAh/cm², at aC-rate of C/2. In some embodiments, the electrochemical cell 100 canhave an area specific capacity of at about least 8 mAh/cm², or at leastabout 9 mAh/cm², at a C-rate of C/2.

In some embodiments, a redox mediator is used to improve the chargetransfer within the semi-solid suspension. In some embodiments, theredox mediator is based on Fe²⁺ or V²⁺, V³⁺, or V⁴⁺. In someembodiments, the redox mediator is ferrocene.

In some embodiments, the conductive particles have shapes, which mayinclude spheres, platelets, or rods to optimize solids packing fraction,increase the semi-solid's net electronic conductivity, and improverheological behavior of semi-solids. In some embodiments, low aspect orsubstantially equiaxed or spherical particles are used to improve theability of the semi-solid to flow under stress.

In some embodiments, the particles have a plurality of sizes so as toincrease packing fraction. In particular, the particle size distributioncan be bi-modal, in which the average particle size of the largerparticle mode is at least 5 times larger than average particle size ofthe smaller particle mode. In some embodiments, the mixture of large andsmall particles improves flow of the material during cell loading andincreases solid volume fraction and packing density in the loaded cell.

In some embodiments, the nature of the semi-solid cathode 140 and/or thesemi-solid anode 150 suspensions can be modified prior to and subsequentto filling of the negative electroactive zone and the positiveelectroactive zone of an electrochemical cell to facilitate flow duringloading and packing density in the loaded cell.

In some embodiments, the particle suspension is initially stabilized byrepulsive interparticle steric forces that arise from surfactantmolecules. After the particle suspension is loaded into the positiveelectroactive zone and/or the negative electroactive zone, chemical orheat treatments can cause these surface molecules to collapse orevaporate and promote densification. In some embodiments, thesuspension's steric forces are modified intermittently during loading.

For example, the particle suspension can be initially stabilized byrepulsive interparticle electrostatic double layer forces to decreaseviscosity. The repulsive force reduces interparticle attraction andreduces agglomeration. After the particle suspension is loaded into thepositive electroactive zone and/or negative electroactive zone, thesurface of the particles can be further modified to reduce interparticlerepulsive forces and thereby promote particle attraction and packing.For example, ionic solutions such as salt solutions can be added to thesuspension to reduce the repulsive forces and promote aggregation anddensification so as to produce increased solids fraction loading afterfilling of the electroactive zones. In some embodiments, salt is addedintermittently during suspension loading to increase density inincremental layers.

In some embodiments, the positive and/or negative electroactive zonesare loaded with a particle suspension that is stabilized by repulsiveforces between particles induced by an electrostatic double layer orshort-range steric forces due to added surfactants or dispersants.Following loading, the particle suspension is aggregated and densifiedby increasing the salt concentration of the suspension. In someembodiments, the salt that is added is a salt of a working ion for thebattery (e.g., a lithium salt for a lithium ion battery) and upon beingadded, causes the liquid phase to become an ion-conducting electrolyte(e.g., for a lithium rechargeable battery, may be one or more alkylcarbonates, or one or more ionic liquids). Upon increasing the saltconcentration, the electrical double layer causing repulsion between theparticles is “collapsed”, and attractive interactions cause the particleto floc, aggregate, consolidate, or otherwise densify. This allows theelectrode of the battery to be formed from the suspension while it has alow viscosity, for example, by pouring, injection, or pumping into thepositive and/or negative electroactive zones that can form a net-shapedelectrode, and then allows particles within the suspension to beconsolidated for improved electrical conduction, higher packing densityand longer shelf life.

In some embodiments, the cathode 140 and/or anode 150 semi-solidsuspensions can initially be flowable, and can be caused to becomenon-flowable by “fixing”. In some embodiments, fixing can be performedby the action of electrochemically cycling the battery. In someembodiments, electrochemical cycling is performed within the current,voltage, or temperature range over which the battery is subsequentlyused. In some embodiments, fixing is performed by electrochemicalcycling of the battery to a higher or lower current, higher or lowervoltage, or higher or lower temperature, that the range over which thebattery is subsequently used. In some embodiments, fixing can beperformed by the action of photopolymerization. In some embodiments,fixing is performed by action of electromagnetic radiation withwavelengths that are transmitted by the unfilled positive and/ornegative electroactive zones of the electrochemical cell 100 formed fromthe semi-solid cathode 140 and/or the semi-solid anode 150. In someembodiments, one or more additives are added to the semi-solidsuspensions to facilitate fixing.

In some embodiments, the injectable and flowable cathode 140 and/oranode 150 semi-solid is caused to become less flowable or more flowableby “plasticizing”. In some embodiments, the rheological properties ofthe injectable and flowable semi-solid suspensions can be modified bythe addition of a thinner, a thickener, and/or a plasticizing agent. Insome embodiments, these agents promote processability and help retaincompositional uniformity of the semi-solid under flowing conditions andpositive and negative electroactive zone filling operations. In someembodiments, one or more additives can be added to the flowablesemi-solid suspension to adjust its flow properties to accommodateprocessing requirements.

Semi-Solid Composition

In some embodiments, the semi-solid cathode 140 and in some embodiments,the anode 150 (e.g., a semi-solid anode) suspensions provide a means toproduce a substance that functions collectively as anion-storage/ion-source, electron conductor, and ionic conductor in asingle medium that acts as a working electrode.

The cathode 140 and/or anode 150 semi-solid ion-storing redoxcomposition as described herein can have, when taken in moles per liter(molarity), at least 10M concentration of redox species. In someembodiments, the cathode 140 and/or the anode 150 semi-solidsion-storing redox composition can include at least 12M, at least 15M, orat least 20M of the redox species. The electrochemically active materialcan be an ion storage material and or any other compound or ion complexthat is capable of undergoing Faradaic reaction in order to storeenergy. The electroactive material can also be a multiphase materialincluding the above described redox-active solid mixed with anon-redox-active phase, including solid-liquid suspensions, orliquid-liquid multiphase mixtures, including micelles or emulsionshaving a liquid ion-storage material intimately mixed with a supportingliquid phase. Systems that utilize various working ions can includeaqueous systems in which Li⁺, Na⁺, or other alkali ions are the workingions, even alkaline earth working ions such as Ca²⁺, Mg²⁺, or Al³⁺. Ineach of these instances, a negative electrode storage material and apositive electrode storage material may be required, the negativeelectrode storing the working ion of interest at a lower absoluteelectrical potential than the positive electrode. The cell voltage canbe determined approximately by the difference in ion-storage potentialsof the two ion-storage electrode materials.

Systems employing negative and/or positive ion-storage materials thatare insoluble storage hosts for working ions, meaning that saidmaterials can take up or release the working ion while all otherconstituents of the materials remain substantially insoluble in theelectrolyte, are particularly advantageous as the electrolyte does notbecome contaminated with electrochemical composition products. Inaddition, systems employing negative and/or positive lithium ion-storagematerials are particularly advantageous when using non-aqueouselectrochemical compositions.

In some embodiments, the semi-solid ion-storing redox compositionsinclude materials proven to work in conventional lithium-ion batteries.In some embodiments, the semi-solid cathode 140 electroactive materialcontains lithium positive electroactive materials and the lithiumcations are shuttled between the anode 150 (e.g., a semi-solid anode)and the semi-solid cathode 140, intercalating into solid, host particlessuspended in a liquid electrolyte.

In some embodiments, at least one of the semi-solid cathode 140 and/oranode 150 (e.g., a semi-solid anode) includes a condensed ion-storingliquid of a redox-active compound, which may be organic or inorganic,and includes but is not limited to lithium metal, sodium metal,lithium-metal alloys, gallium and indium alloys with or withoutdissolved lithium, molten transition metal chlorides, thionyl chloride,and the like, or redox polymers and organics that can be liquid underthe operating conditions of the battery. Such a liquid form may also bediluted by or mixed with another, non-redox-active liquid that is adiluent or solvent, including mixing with such diluents to form alower-melting liquid phase. In some embodiments, the redox-activecomponent can comprise, by mass, at least 10% of the total mass of theelectrolyte. In other embodiments, the redox-active component willcomprise, by mass, between approximately 10% and 25% of the total massof the electrolyte. In some embodiments, the redox-active component willcomprise by mass, at least 25% or more of the total mass of theelectrolyte.

In some embodiments, the redox-active electrode material, whether usedas a semi-solid or a condensed liquid format as defined above, comprisesan organic redox compound that stores the working ion of interest at apotential useful for either the positive or negative electrode of abattery. Such organic redox-active storage materials include “p”-dopedconductive polymers such as polyaniline or polyacetylene basedmaterials, polynitroxide or organic radical electrodes (such as thosedescribed in: H. Nishide et al., Electrochim. Acta, 50, 827-831, (2004),and K. Nakahara, et al., Chem. Phys. Lett., 359, 351-354 (2002)),carbonyl based organics, and oxocarbons and carboxylate, includingcompounds such as Li₂C₆O₆, Li₂C₈H₄O₄, and Li₂C₆H₄O₄ (see for example M.Armand et al., Nature Materials, DOI: 10.1038/nmat2372) and organosulfurcompounds.

In some embodiments, organic redox compounds that are electronicallyinsulating are used. In some instance, the redox compounds are in acondensed liquid phase such as liquid or flowable polymers that areelectronically insulating. In such cases, the redox active slurry may ormay not contain an additional carrier liquid. Additives can be combinedwith the condensed phase liquid redox compound to increase electronicconductivity. In some embodiments, such electronically insulatingorganic redox compounds are rendered electrochemically active by mixingor blending with particulates of an electronically conductive material,such as solid inorganic conductive materials including but not limitedto metals, metal carbides, metal nitrides, metal oxides, and allotropesof carbon including carbon black, graphitic carbon, carbon fibers,carbon microfibers, vapor-grown carbon fibers (VGCF), fullerenic carbonsincluding “buckyballs”, carbon nanotubes (CNTs), multiwall carbonnanotubes (MWNTs), single wall carbon nanotubes (SWNTs), graphene sheetsor aggregates of graphene sheets, and materials comprising fullerenicfragments.

In some embodiments, such electronically insulating organic redoxcompounds are rendered electronically active by mixing or blending withan electronically conductive polymer, including but not limited topolyaniline or polyacetylene based conductive polymers orpoly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole, polythiophene,poly(p-phenylene), poly(triphenylene), polyazulene, polyfluorene,polynaphtalene, polyanthracene, polyfuran, polycarbazole,tetrathiafulvalene-substituted polystyrene, ferrocene-substitutedpolyethylene, carbazole-substituted polyethylene, polyoxyphenazine,polyacenes, or poly(heteroacenes). The conductive additives form anelectrically conducting framework within the insulating liquid redoxcompounds that significantly increases the electrically conductivity ofthe composition. In some embodiments, the conductive addition forms apercolative pathway to the current collector. In some embodiments theredox-active electrode material comprises a sol or gel, including forexample metal oxide sols or gels produced by the hydrolysis of metalalkoxides, amongst other methods generally known as “sol-gelprocessing.” Vanadium oxide gels of composition V_(x)O_(y) are amongstsuch redox-active sol-gel materials.

Other suitable positive active materials for use in the semi-solidcathode 140 include solid compounds known to those skilled in the art asthose used in NiMH (Nickel-Metal Hydride) Nickel Cadmium (NiCd)batteries. Still other positive electrode compounds for Li storageinclude those used in carbon monofluoride batteries, generally referredto as CF_(x), or metal fluoride compounds having approximatestoichiometry MF₂ or MF₃ where M comprises, for example, Fe, Bi, Ni, Co,Ti, or V. Examples include those described in H. Li, P. Balaya, and J.Maier, Li-Storage via Heterogeneous Reaction in Selected Binary MetalFluorides and Oxides, Journal of The Electrochemical Society, 151 [11]A1878-A1885 (2004), M. Bervas, A. N. Mansour, W.-S. Woon, J. F.Al-Sharab, F. Badway, F. Cosandey, L. C. Klein, and G. G. Amatucci,“Investigation of the Lithiation and Delithiation Conversion Mechanismsin a Bismuth Fluoride Nanocomposites”, J. Electrochem. Soc., 153, A799(2006), and I. Plitz, F. Badway, J. Al-Sharab, A. DuPasquier, F.Cosandey and G. G. Amatucci, “Structure and Electrochemistry ofCarbon-Metal Fluoride Nanocomposites Fabricated by a Solid State RedoxConversion Reaction”, J. Electrochem. Soc., 152, A307 (2005).

As another example, fullerenic carbon including single-wall carbonnanotubes (SWNTs), multiwall carbon nanotubes (MWNTs), or metal ormetalloid nanowires may be used as ion-storage materials. One example isthe silicon nanowires used as a high energy density storage material ina report by C. K. Chan, H. Peng, G. Liu, K. Mcllwrath, X. F. Zhang, R.A. Huggins, and Y. Cui, High-performance lithium battery anodes usingsilicon nanowires, Nature Nanotechnoloy, published online 16 Dec. 2007;doi:10.1038/nnano.2007.411. In some embodiments, electroactive materialsfor the semi-solid cathode 140 in a lithium system can include thegeneral family of ordered rocksalt compounds LiMO₂ including thosehaving the α-NaFeO₂ (so-called “layered compounds”) ororthorhombic-LiMnO₂ structure type or their derivatives of differentcrystal symmetry, atomic ordering, or partial substitution for themetals or oxygen. M comprises at least one first-row transition metalbut may include non-transition metals including but not limited to Al,Ca, Mg, or Zr. Examples of such compounds include LiCoO₂, LiCoO₂ dopedwith Mg, LiNiO₂, Li(Ni, Co, Al)O₂ (known as “NCA”) and Li(Ni, Mn, Co)O₂(known as “NMC”). Other families of exemplary cathode 140 electroactivematerials includes those of spinel structure, such as LiMn₂O₄ and itsderivatives, so-called “layered-spinel nanocomposites” in which thestructure includes nanoscopic regions having ordered rocksalt and spinelordering, olivines LiMPO₄ and their derivatives, in which M comprisesone or more of Mn, Fe, Co, or Ni, partially fluorinated compounds suchas LiVPO₄F, other “polyanion” compounds as described below, and vanadiumoxides V_(x)O_(y) including V₂O₅ and V₆O₁₁.

In some embodiments, the semi-solid cathode 140 electroactive materialcomprises a transition metal polyanion compound, for example asdescribed in U.S. Pat. No. 7,338,734. In some embodiments the activematerial comprises an alkali metal transition metal oxide or phosphate,and for example, the compound has a compositionA_(x)(M′_(1-a)M″_(a))_(y)(XD₄)_(z)A_(x)(M′_(1-a)M″_(a))_(y)(DXD₄)_(z),or A_(x)(M′_(1-a)M″_(a))_(y)(X₂D₇)₇, and have values such that x, plusy(1-a) times a formal valence or valences of M′, plus ya times a formalvalence or valence of M″, is equal to z times a formal valence of theXD₄, X₂D₇, or DXD₄ group; or a compound comprising a composition(A_(1-a)M″_(a))_(x)M′_(y)(XD₄)_(z),(A_(1-a)M″_(a))_(x)M′_(y)(DXD₄)z(A_(1-a)M″_(a))_(x)M′_(y)(X₂D₇)_(z), andhave values such that (1-a)x plus the quantity ax times the formalvalence or valences of M″ plus y times the formal valence or valences ofM′ is equal to z times the formal valence of the XD₄, X₂D₇ or DXD₄group. In the compound, A is at least one of an alkali metal andhydrogen, M′ is a first-row transition metal, X is at least one ofphosphorus, sulfur, arsenic, molybdenum, and tungsten, M″ any of a GroupIIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIBmetal, D is at least one of oxygen, nitrogen, carbon, or a halogen. Thepositive electroactive material can be an olivine structure compoundLiMPO₄, where M is one or more of V, Cr, Mn, Fe, Co, and Ni, in whichthe compound is optionally doped at the Li, M or O-sites. Deficienciesat the Li-site are compensated by the addition of a metal or metalloid,and deficiencies at the O-site are compensated by the addition of ahalogen. In some embodiments, the positive active material comprises athermally stable, transition-metal-doped lithium transition metalphosphate having the olivine structure and having the formula(Li_(1-x)Z_(x))MPO₄, where M is one or more of V, Cr, Mn, Fe, Co, andNi, and Z is a non-alkali metal dopant such as one or more of Ti, Zr,Nb, Al, or Mg, and x ranges from 0.005 to 0.05.

In other embodiments, the lithium transition metal phosphate materialhas an overall composition of Li_(1-x-z)M_(1-z)PO₄, where M comprises atleast one first row transition metal selected from the group consistingof Ti, V, Cr, Mn, Fe, Co and Ni, where x is from 0 to 1 and z can bepositive or negative. M includes Fe, z is between about 0.15-0.15. Thematerial can exhibit a solid solution over a composition range of0<x<0.15, or the material can exhibit a stable solid solution over acomposition range of x between 0 and at least about 0.05, or thematerial can exhibit a stable solid solution over a composition range ofx between 0 and at least about 0.07 at room temperature (22-25° C.). Thematerial may also exhibit a solid solution in the lithium-poor regime,e.g., where x≥0.8, or x≥0.9, or x≥0.95.

In some embodiments the redox-active electrode material comprises ametal salt that stores an alkali ion by undergoing a displacement orconversion reaction. Examples of such compounds include metal oxidessuch as CoO, Co₃O₄, NiO, CuO, MnO, typically used as a negativeelectrode in a lithium battery, which upon reaction with Li undergo adisplacement or conversion reaction to form a mixture of Li₂O and themetal constituent in the form of a more reduced oxide or the metallicform. Other examples include metal fluorides such as CuF₂, FeF₂, FeF₃,BiF₃, CoF₂, and NiF₂, which undergo a displacement or conversionreaction to form LiF and the reduced metal constituent. Such fluoridesmay be used as the positive electrode in a lithium battery. In otherembodiments, the redox-active electrode material comprises carbonmonofluoride or its derivatives. In some embodiments the materialundergoing displacement or conversion reaction is in the form ofparticulates having on average dimensions of 100 nanometers or less. Insome embodiments the material undergoing displacement or conversionreaction comprises a nanocomposite of the active material mixed with aninactive host, including but not limited to conductive and relativelyductile compounds such as carbon, or a metal, or a metal sulfide. FeS₂and FeF₃ can also be used as cheap and electronically conductive activematerials in a nonaqueous or aqueous lithium system. In someembodiments, a CF_(x) electrode, FeS₂ electrode, or MnO₂ electrode is apositive electrode used with a lithium metal negative electrode toproduce a lithium battery. In some embodiments, such battery is aprimary battery. In some embodiments, such battery is a rechargeablebattery.

In some embodiments, the working ion is selected from the groupconsisting of Li⁺, Na⁺, H⁺, Mg²⁺, Al³⁺, or Ca²⁺.

In some embodiments, the working ion is selected from the groupconsisting of Li⁺ or Na⁺.

In some embodiments, the semi-solid ion-storing redox compositionincludes a solid including an ion-storage compound.

In some embodiments, the ion is proton or hydroxyl ion and the ionstorage compound includes those used in a nickel-cadmium or nickel metalhydride battery.

In some embodiments, the ion is lithium and the ion storage compound isselected from the group consisting of metal fluorides such as CuF₂,FeF₂, FeF₃, BiF₃, CoF₂, and NiF₂.

In some embodiments, the ion is lithium and the ion storage compound isselected from the group consisting of metal oxides such as CoO, Co₃O₄,NiO, CuO, MnO.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from compounds with formula(Li_(1-x)Z_(x))MPO₄, where M is one or more of V, Cr, Mn, Fe, Co, andNi, and Z is a non-alkali metal dopant such as one or more of Ti, Zr,Nb, Al, or Mg, and x ranges from 0.005 to 0.05.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from compounds with formulaLiMPO₄, where M is one or more of V, Cr, Mn, Fe, Co, and Ni, in whichthe compound is optionally doped at the Li, M or O-sites.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from the group consisting ofA_(x)(M′_(1-a)M″_(a))_(y)(XD₄)_(z), A_(x)(M′_(1-a)M″_(a))_(y)(DXD₄)_(z),and A_(x)(M′_(1-a)M″_(a))_(y)(X₂D₇)_(z), wherein x, plus y(1-a) times aformal valence or valences of M′, plus ya times a formal valence orvalence of M″, is equal to z times a formal valence of the XD₄, X₂D₇, orDXD₄ group; and A is at least one of an alkali metal and hydrogen, M′ isa first-row transition metal, X is at least one of phosphorus, sulfur,arsenic, molybdenum, and tungsten, M″ any of a Group IIA, IIIA, IVA, VA,VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIB metal, D is at leastone of oxygen, nitrogen, carbon, or a halogen.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from the group consisting ofA_(1-a)M″)_(x)M′_(y)(XD₄)_(z), (A_(1-a)M″_(a))_(x)M′_(y)(DXD₄)z andA_(1-a)M″_(a))_(x)M′_(y)(X₂D₇)_(z), where (1-a)x plus the quantity axtimes the formal valence or valences of M″ plus y times the formalvalence or valences of M′ is equal to z times the formal valence of theXD₄, X₂D₇ or DXD₄ group, and A is at least one of an alkali metal andhydrogen, M′ is a first-row transition metal, X is at least one ofphosphorus, sulfur, arsenic, molybdenum, and tungsten, M″ any of a GroupIIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIBmetal, D is at least one of oxygen, nitrogen, carbon, or a halogen.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from the group consisting ofordered rocksalt compounds LiMO₂ including those having the α-NaFeO₂ andorthorhombic-LiMnO₂ structure type or their derivatives of differentcrystal symmetry, atomic ordering, or partial substitution for themetals or oxygen, where M includes at least one first-row transitionmetal but may include non-transition metals including but not limited toAl, Ca, Mg or Zr.

In some embodiments, the semi-solid ion storing redox compositionincludes a solid including amorphous carbon, disordered carbon,graphitic carbon, or a metal-coated or metal decorated carbon.

In some embodiments, the semi-solid ion storing redox composition caninclude a solid including nanostructures, for example, nanowires,nanorods, and nanotetrapods.

In some embodiments, the semi-solid ion storing redox compositionincludes a solid including an organic redox compound.

In some embodiments, the positive electrode can include a semi-solid ionstoring redox composition including a solid selected from the groupsconsisting of ordered rocksalt compounds LiMO₂ including those havingthe α-NaFeO₂ and orthorhombic-LiMnO₂ structure type or their derivativesof different crystal symmetry, atomic ordering, or partial substitutionfor the metals or oxygen, wherein M Includes at least one first-rowtransition metal but may include non-transition metals including but notlimited to Al, Ca, Mg, or Zr. The anode 150 can include a semi-solidion-storing composition including a solid selected from the groupconsisting of amorphous carbon, disordered carbon, graphitic carbon, ora metal-coated or metal-decorated carbon.

In some embodiments, the semi-solid cathode 140 can include a semi-solidion-storing redox composition such as, for example, a solid selectedfrom the group consisting of A_(x)(M′_(1-a)M″_(a))_(y)(XD₄)_(z),A_(x)(M′_(1-a)M″_(a))_(y)(DX D₄)_(z), andA_(x)(M′_(1-a)M″_(a))_(y)(X₂D₇)_(z), and where x, plus y(1-a) times aformal valence or valences of M′, plus ya times a formal valence orvalence of M″, is equal to z times a formal valence of the XD₄, X₂D₇, orDXD₄ group, and A is at least one of an alkali metal and hydrogen, M′ isa first-row transition metal, X is at least one of phosphorus, sulfur,arsenic, molybdenum, and tungsten, M″ any of a Group IIA, IIIA, IVA, VA,VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIB metal, D is at leastone of oxygen, nitrogen, carbon, or a halogen. In some embodiments, theanode 150 can be semi-solid anode which includes a semi-solidion-storing redox composition such as, for example, a solid selectedfrom the group consisting of amorphous carbon, disordered carbon,graphitic carbon, or a metal-coated or metal-decorated carbon. In someembodiments, the anode 150 can include a semi-solid ion-storing redoxcomposition including a compound with a spinel structure.

In some embodiments, the semi-solid cathode 140 can include a semi-solidion-storing redox composition such as, for example, a compound selectedfrom the group consisting of LiMn₂O₄ and its derivatives; layered-spinelnanocomposites in which the structure includes nanoscopic regions havingordered rocksalt and spinel ordering; so-called “high voltage spinels”with a potential vs. Li/Li+ that exceeds 4.3V including but not limitedto LiNi_(0.5)Mn_(1.5)O₄; olivines LiMPO₄ and their derivatives, in whichM includes one or more of Mn, Fe, Co, or Ni, partially fluorinatedcompounds such as LiVPO₄F, other “polyanion” compounds, and vanadiumoxides V_(x)O_(y) including V₂O₅ and V₆O₁₁.

In some embodiments the semi-solid battery is a lithium battery, and theanode 150 compound includes graphite, graphitic or non-graphitic carbon,amorphous carbon, mesocarbon microbeads, boron-carbon alloys, hard ordisordered carbon, lithium titanate spinel, or a solid metal or metalalloy or metalloid or metalloid alloy that reacts with lithium to formintermetallic compounds, e.g., Si, Ge, Sn, Bi, Zn, Ag, Al, any othersuitable metal alloy, metalloid alloy or combination thereof, or alithiated metal or metal alloy including such compounds as LiAl, Li₉Al₄,Li₃Al, LiZn, LiAg, Li₁₀Ag₃, Li₅B₄, Li₇B₆, Li₁₂Si₇, Li₂₁Si₈, Li₁₃Si₄,Li₂₁Si₅, Li₅Sn₂, Li₁₃Sn₅, Li₇Sn₂, Li₂₂Sn₅, Li₂Sb, Li₃Sb, LiBi, or Li₃Bi,or amorphous metal alloys of lithiated or non-lithiated compositions,any other materials or alloys thereof, or any other combination thereof.

In some embodiments, the electrochemical function of the electrochemicalcell 100 can be improved by mixing or blending the semi-solid cathode140 and/or the semi-solid anode 150 particles with particulates of anelectronically conductive material, such as solid inorganic conductivematerials including but not limited to metals, metal carbides, metalnitrides, metal oxides, and allotropes of carbon including carbon black,graphitic carbon, carbon fibers, carbon microfibers, vapor-grown carbonfibers (VGCF), fullerenic carbons including “buckyballs”, carbonnanotubes (CNTs), multiwall carbon nanotubes (MWNTs), single wall carbonnanotubes (SWNTs), graphene sheets or aggregates of graphene sheets, andmaterials comprising fullerenic fragments. In some embodiments, suchelectronically insulating organic redox compounds are renderedelectronically active by mixing or blending with an electronicallyconductive polymer, including but not limited to polyanilinc orpolyacetylene based conductive polymers orpoly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole, polythiophene,poly(p-phenylene), poly(triphenylene), polyazulene, polyfluorene,polynaphtalene, polyanthracene, polyfuran, polycarbazole,tetrathiafulvalene-substituted polystyrene, ferrocene-substitutedpolyethylene, carbazole-substituted polyethylene, polyoxyphenazine,polyacenes, or poly(heteroacenes).). In some embodiments, the resultingsemi-solid cathode 140 and/or semi-solid anode 150 mixture has anelectronic conductivity of at least about 10⁻³ S/cm, of at least about10⁻² S/cm or more.

In some embodiments, the particles included in the semi-solid cathode140 and/or semi-solid anode 150 can be configured to have a partial orfull conductive coating.

In some embodiments, the semi-solid ion-storing redox compositionincludes an ion-storing solid coated with a conductive coating material.In some embodiments, the conductive coating material has higher electronconductivity than the solid. In some embodiments, the solid is graphiteand the conductive coating material is a metal, metal carbide, metaloxide, metal nitride, or carbon. In some embodiments, the metal iscopper.

In some embodiments, the solid of the semi-solid ion-storing material iscoated with metal that is redox inert at the operating conditions of theredox energy storage device. In some embodiments, the solid of thesemi-solid ion storing material is coated with copper to increase theconductivity of the storage material particle, to increase the netconductivity of the semi-solid, and/or to facilitate charge transferbetween energy storage particles and conductive additives. In someembodiments, the storage material particle is coated with, about 1.5% byweight metallic copper. In some embodiments, the storage materialparticle is coated with about 3.0% by weight metallic copper. In someembodiments, the storage material particle is coated with about 8.5% byweight metallic copper. In some embodiments, the storage materialparticle is coated with about 10.0% by weight metallic copper. In someembodiments, the storage material particle is coated with about 15.0% byweight metallic copper. In some embodiments, the storage materialparticle is coated with about 20.0% by weight metallic copper.

In some embodiments, the conductive coating is placed on the semi-solidcathode 140 and/or anode 150 particles by chemical precipitation of theconductive element and subsequent drying and/or calcination.

In some embodiments, the conductive coating is placed on the semi-solidcathode 140 and/or anode 150 particles by electroplating (e.g., within afluidized bed).

In some embodiments, the conductive coating is placed on the semi-solidcathode 140 and/or anode 150 particles by co-sintering with a conductivecompound and subsequent comminution.

In some embodiments, the electrochemically active particles have acontinuous intraparticle conductive material or are embedded in aconductive matrix.

In some embodiments, a conductive coating and intraparticulateconductive network is produced by multicomponent-spray-drying, asemi-solid cathode 140 and/or anode 150 particles and conductivematerial particulates.

In some embodiments, the semi-solid composition (e.g., the semi-solidcathode 140 composition or the semi-solid anode 150 composition) alsoincludes conductive polymers that provide an electronically conductiveelement. In some embodiments, the conductive polymers can include one ormore of a polyacetylene, polyaniline, polythiophene, polypyrrole,poly(p-phenylene), poly(triphenylene), polyazulene, polyfluorene,polynaphtalene, polyanthracene, polyfuran, polycarbazole, polyacenes,poly(heteroacenes). In some embodiments, the conductive polymer can be acompound that reacts in-situ to form a conductive polymer on the surfaceof the active material particles. In some embodiments, the compound canbe 2-hexylthiophene or 3-hexylthiophene and oxidizes during charging ofthe battery to form a conductive polymer coating on solid particles inthe cathode semi-solid suspension. In other embodiments, redox activematerial can be embedded in conductive matrix. The redox active materialcan coat the exterior and interior interfaces in a flocculated oragglomerated particulate of conductive material. In some embodiments,the redox-active material and the conductive material can be twocomponents of a composite particulate. Without being bound by any theoryor mode of operation, such coatings can pacify the redox activeparticles and can help prevent undesirable reactions with carrier liquidor electrolyte. As such, it can serve as a synthetic solid-electrolyteinterphase (SEI) layer.

In some embodiments, inexpensive iron compounds such as pyrite (FeS₂)are used as inherently electronically conductive ion storage compounds.In some embodiments, the ion that is stored is Li⁺.

In some embodiments, redox mediators are added to the semi-solid toimprove the rate of charge transfer within the semi-solid electrode. Insome embodiments, this redox mediator is ferrocene or aferrocene-containing polymer. In some embodiments, the redox mediator isone or more of tetrathiafulvalene-substituted polystyrene,ferrocene-substituted polyethylene, carbazole-substituted polyethylene.

In some embodiments, the surface conductivity or charge transferresistance of the positive current collectors 110 and/or the negativecurrent collector 120 included in the electrochemical cell 100 isincreased by coating the current collector surface with a conductivematerial. Such layers can also serve as a synthetic SEI layer.Non-limiting examples of conductive coating materials include carbon, ametal, metal-carbide, metal nitride, metal oxide, or conductive polymer.In some embodiments, the conductive polymer includes but is not limitedto polyaniline or polyacetylene based conductive polymers orpoly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole, polythiophene,poly(p-phenylene), poly(triphenylene), polyazulene, polyfluorene,polynaphtalene, polyanthracene, polyfuran, polycarbazole,tetrathiafulvalene-substituted polystyrene, ferrocene-substitutedpolyethylene, carbazole-substituted polyethylene, polyoxyphenazine,polyacenes, or poly(heteroacenes). In some embodiments, the conductivepolymer is a compound that reacts in-situ to form a conductive polymeron the surface of the current collector. In some embodiments, thecompound is 2-hexylthiophene and oxidizes at a high potential to form aconductive polymer coating on the current collector. In someembodiments; the current collector is coated with metal that isredox-inert at the operating conditions of the redox energy storagedevice.

The semi-solid redox compositions can include various additives toimprove the performance of the redox cell. The liquid phase of thesemi-solids in such instances would comprise a solvent, in which isdissolved an electrolyte salt, and binders, thickeners, or otheradditives added to improve stability, reduce gas formation, improve SEIformation on the negative electrode particles, and the like. Examples ofsuch additives included vinylene carbonate (VC), vinylethylene carbonate(VEC), fluoroethylene carbonate (FEC), or alkyl cinnamates, to provide astable passivation layer on the anode or thin passivation layer on theoxide cathode, propane sultone (PS), propene sultone (PrS), or ethylenethiocarbonate as antigassing agents, biphenyl (BP), cyclohexylbenzene,or partially hydrogenated terphenyls, as gassing/safety/cathodepolymerization agents, or lithium bis(oxatlato)borate as an anodepassivation agent.

In some embodiments, the semi-solid cathode 140 and/or anode 150 caninclude a non-aqueous liquid electrolyte that can include polar solventssuch as, for example, alcohols or aprotic organic solvents. Numerousorganic solvents have been proposed as the components of Li-ion batteryelectrolytes, notably a family of cyclic carbonate esters such asethylene carbonate, propylene carbonate, butylene carbonate, and theirchlorinated or fluorinated derivatives, and a family of acyclic dialkylcarbonate esters, such as dimethyl carbonate, diethyl carbonate,ethylmethyl carbonate, dipropyl carbonate, methyl propyl carbonate,ethyl propyl carbonate, dibutyl carbonate, butylmethyl carbonate,butylethyl carbonate and butylpropyl carbonate. Other solvents proposedas components of Li-ion battery electrolyte solutions includey-butyrolactone, dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether,sulfolane, methylsulfolane, acetonitrile, propiononitrile, ethylacetate, methyl propionate, ethyl propionate, dimethyl carbonate,tetraglyme, and the like. These nonaqueous solvents are typically usedas multicomponent mixtures, into which a salt is dissolved to provideionic conductivity. Exemplary salts to provide lithium conductivityinclude LiClO₄, LiPF₆, LiBF₄, LiTFSI, LiBETI, LiBOB, and the like.

In some embodiments, the non-aqueous cathode 140 and/or anode 150semi-solid compositions are prevented from absorbing impurity water andgenerating acid (such as HF in the case of LiPF₆ salt) by incorporatingcompounds that getter water into the active material suspension, or intothe storage tanks or other plumbing of the system, for example, in thecase of redox flow cell batteries. Optionally, the additives are basicoxides that neutralize the acid. Such compounds include but are notlimited to silica gel, calcium sulfate (for example, the product knownas Drierite), aluminum oxide and aluminum hydroxide.

In some embodiment, the cathode 140 can be a semi-solid cathode and theanode 150 can be a conventional anode for example, a solid anode formedfrom the calendering process as is commonly known in the arts. In someembodiments, the cathode 140 can be a semi-solid cathode and the anode150 can also be a semi-solid anode as described herein. In someembodiments, the cathode 140 and the anode 150 can both be semi-solidflowable electrodes, for example, for use in a redox flow cell.

In some embodiments, the semi-solid cathode 140 and the semi-solid anode150 can be prepared by combining a quantity of an active material withan electrolyte and a conductive material, and mixing until asubstantially stable suspension forms that has a mixing index of atleast about 0.9, at least about 0.95, or at least about 0.975, inclusiveof all ranges therebetween. In some embodiments, the semi-solid cathode140 and/or the semi-solid anode 150 material is mixed until theelectrode material has an electronic conductivity of at least about 10⁻³S/cm, or at least about 10⁻² S/cm, inclusive of all ranges therebetween.In some embodiments, the electrode material is mixed until the electrodematerial has an apparent viscosity of less than about 25,000 Pa·s, lessthan about 10,000 Pa·s, less than about 1,000 Pa·s, or less than about100 Pa·s at an apparent shear rate of about 5 s⁻¹, inclusive of allranges therebetween. In such embodiments, the semi-solid cathode 140 caninclude about 35-75 vol % of active material and about 0.5-8 vol % ofconductive material, and the semi-solid anode 150 can include about35-75 vol % of active material and about 0-10 vol % of conductivematerial. Furthermore, the electrochemical cell 100 that includes thesemi-solid cathode 140 and/or the semi-solid anode 150 can have an areaspecific capacity of at least about 7 mAh/cm², for example, at leastabout 8 mAh/cm², at least about 9 mAh/cm², or at least about 10 mAh/cm².In some embodiments, the active material included in the semi-solidcathode 140 can be LFP. In such embodiments, the electrochemical 100 canhave an area specific capacity of at least about 7 mAh/cm² at a C-rateof C/4. In some embodiments, the active material included in thesemi-solid cathode can be NMC. In such embodiments, the electrochemicalcell 100 can have an area specific capacity of at least about 7 mAh/cm²at a C-rate of C/4.

In some embodiments, the mixing of the electrode material (e.g., thesemi-solid cathode 140 or the semi-solid anode 150) can be performedwith, for example, any one of a high shear mixer, a planetary mixer, acentrifugal planetary mixture, a sigma mixture, a CAM mixture and/or aroller mixture. In some embodiments, the mixing of the electrodematerial can supply a specific mixing energy of at least about 90 J/g,at least about 100 J/g, about 90 J/g to about 150 J/g, or about 100 J/gto about 120 J/g, inclusive of all ranges therebetween.

In some embodiments, the composition of the electrode material and themixing process can be selected to homogeneously disperse the componentsof the slurry, achieve a percolating conductive network throughout theslurry and sufficiently high bulk electrical conductivity, whichcorrelates to desirable electrochemical performance as described infurther detail herein, to obtain a rheological state conducive toprocessing, which may include transfer, conveyance (e.g., extrusion),dispensing, segmenting or cutting, and post-dispense forming (e.g.,press forming, rolling, calendering, etc.), or any combination thereof.

During mixing, the compositional homogeneity of the slurry willgenerally increase with mixing time, although the microstructure of theslurry may be changing as well. The compositional homogeneity of theslurry suspension can be evaluated quantitatively by an experimentalmethod based on measuring statistical variance in the concentrationdistributions of the components of the slurry suspension. For example,mixing index is a statistical measure, essentially a normalized varianceor standard deviation, describing the degree of homogeneity of acomposition. (See, e.g., Erol, M, & Kalyon, D. M., Assessment of theDegree of Mixedness of Filled Polymers, Intern. Polymer Processing XX(2005) 3, pps. 228-237). Complete segregation would have a mixing indexof zero and a perfectly homogeneous mix a mixing index of one.Alternatively, the homogeneity of the slurry can be described by itscompositional uniformity (+x %/−y %), defined herein as the range:(100%−y)*C to (100%+x)*C. All of the values x and y are thus defined bythe samples exhibiting maximum positive and negative deviations from themean value C, thus the compositions of all mixed material samples takenfall within this range.

The basic process of determining mixing index includes taking a numberof equally and appropriately sized material samples from the aggregatedmix and conducting compositional analysis on each of the samples. Thesampling and analysis can be repeated at different times in the mixingprocess. The sample size and volume is based on considerations of lengthscales over which homogeneity is important, for example, greater than amultiple of both the largest solid particle size and the ultimate mixedstate average intra-particle distance at the low end, and 1/Nth of thetotal volume where N is the number of samples at the high end.Optionally, the samples can be on the order of the electrode thickness,which is generally much smaller than the length and width of theelectrode. Capabilities of certain experimental equipment, such as athermo-gravimetric analyzer (TGA), will narrow the practical samplevolume range further. Sample “dimension” means the cube root of samplevolume. For, example, a common approach to validating the sampling(number of samples) is that the mean composition of the samplescorresponding to a given mixing duration matches the overall portions ofmaterial components introduced to the mixer to a specified tolerance.The mixing index at a given mixing time is defined, according to thepresent embodiments, to be equal to 1σ/σ_(ref), where σ is the standarddeviation in the measured composition (which may be the measured amountof any one or more constituents of the slurry) and σ_(ref) is equal to[C(1-C)]^(1/2), where C is the mean composition of the N samples, so asthe variation in sample compositions is reduced, the mixing indexapproaches unity. It should be understood in the above description that“time” and “duration” are general terms speaking to the progression ofthe mixing event.

In one embodiment, a total sample volume of 43 cubic centimeterscontaining 50% by volume active material powder with a particle sizedistribution with D50=10 um and D90=15 um, and 6% by volume conductiveadditive agglomerates powder with D50=8 um and D90=12 um in organicsolvent is prepared. This mixture can, for example, be used to buildelectrodes with an area of 80 cm², and a thickness of 500 μm. The sampledimension should be larger than the larger solid particle size, i.e., 15μm, and also the larger mixed state intra-particle length scale, i.e.,about 16 μm, by a predetermined factor. With a target of N=14 samples,the sample dimension should be less than 2,500 μm. The specificdimension of interest is in the middle of this range, i.e., 500 μm.Accordingly, to quantify mixing index, the samples are taken with aspecial tool having a cylindrical sampling cavity with a diameter of 0.5mm and a depth of 0.61 mm. In this example, the sample volume would be0.12 mm³.

In some embodiments, the sample volume selection for mixing indexmeasurement is guided by length scales over which uniformity isimportant. In some embodiments, this length scale is the thickness(e.g., 250 μm to 2,000 μm) of an electrode in which the slurry will beused. For example, if the electrode is 0.5 mm thick, the sample volumeshould preferably be on the order of (0.5 mm)³=0.125 mm³, i.e. betweenabout 0.04 mm³ and about 0.4 mm³. If the electrode is 0.2 mm thick, thesample volume should preferably be between 0.0025 and 0.025 mm³. If theelectrode is 2.0 mm thick, the sample volume should preferably bebetween 2.5 mm³ and 25 mm³. In some embodiments, the sample volume bywhich mixing index is evaluated is the cube of the electrode thickness±10%. In some embodiments, the sample volume by which mixing index isevaluated is 0.12 mm³±10%. In one embodiment, the mixing index ismeasured by taking N samples where N is at least 9, each sample havingthe sample volume, from a batch of the electrode slurry or from a formedslurry electrode that has a volume greater than the total volume of theN samples. Each of the sample volumes is heated in a thermo gravimetricanalyzer (TGA) under flowing oxygen gas according to a time-temperatureprofile wherein there is 3 minute hold at room temperature, followed byheating at 20° C./min to 850° C., with the cumulative weight lossbetween 150° C. and 600° C. being used to calculate the mixing index.Measured in this manner, the electrolyte solvents are evaporated and themeasured weight loss is primarily that due to pyrolysis of carbon in thesample volume.

As described herein, conductive additives can have technicalcharacteristics and morphologies (i.e., hierarchical clustering offundamental particles) that influence their dispersive andelectrochemical behavior in dynamic and/or static suspensions.Characteristics that can influence dispersive and electrochemicalbehavior of conductive additives include surface area and bulkconductivity. For example, in the case of certain conductive carbonadditives, morphological factors can impact the dispersion of the carbonparticles. The primary carbon particles have dimensions on the order ofnanometers, the particles typically exist as members of largeraggregates, consisting of particles either electrically bound (e.g., byVan der Waals forces) or sintered together. Such agglomerates may havedimensions on the order of nanometers to microns. Additionally,depending on the surface energies of the particles, environment, and/ortemperature, aggregates can form larger scale clusters commonly referredto as agglomerates, which can have dimensions on the order of microns totens of microns.

When such conductive additives are included in a slurry, fluid shearingforces, e.g., imparted during mixing, can disrupt the carbon network,for example, by overcoming agglomerate and aggregate binding forces. Bydisrupting the conductive network, the additives can be present in afiner scale (more granular and more homogeneous) dispersion of theconductive solid. Mixing can also densify clusters of the conductivesolid. In some embodiments, mixing can both disrupt the conductivenetwork and densify clusters, which can sever electrical conductionpathways and adversely impact electrochemical performance.

FIG. 2A-2C are schematic diagrams of an electrochemically active slurrycontaining active material 310 and conductive additive 320 in which thequantity of the conductive additive 320 is not enough to form aconductive network. FIG. 2A depicts a slurry before any mixing energyhas been applied or after only minimal mixing energy has been applied.FIG. 2B depicts the slurry with an optimal amount of mixing energyapplied and FIG. 2C depicts the slurry with an excessive amount ofmixing energy applied. As illustrated in FIG. 2B even with the optimalamount of mixing, the amount of conductive additive 320 is not adequateto create an appreciable conductive network throughout the electrodevolume.

FIG. 3A-3C are schematic diagrams of an electrochemical active slurriescontaining an active material 410 and conductive additive 420. Contraryto FIG. 2A-C, in this example the quantity of the conductive additive420 is enough to form a conductive network. As shown in FIG. 3A, theconductive additive 420 is largely in the form of unbranchedagglomerates 430. The homogeneity of the conductive additive 420 couldbe characterized as non-uniform at this stage. As shown in FIG. 3B, theagglomerates 430 have been “broken up” by fluid shearing and/or mixingforces and have created the desired “wiring” of the conductive additiveagglomerate 440 interparticle network (also referred to herein as“conductive pathway”). As shown in FIG. 3C, the conductive network hasbeen disrupted by over mixing and the conductive additive 420 is now inthe form of broken and/or incomplete (or non-conductive) pathways 450.Thus, FIGS. 2A-C and FIGS. 3A-C illustrate that an electrochemicallyactive slurry can include a minimum threshold of conductive additive320/420 loading, and an optimal processing regime between two extremes(i.e., the slurry depicted in FIG. 3B). By selecting an appropriateloading of conductive additive 320/420 and processing regime, asemi-solid suspension can be formed having an appreciable conductiveinterparticle network (e.g., conductive additive agglomerate 440network). In some embodiments, the specific mixing energy applied can beabout 90 J/g to about 150 J/g, e.g., at least about 90 J/g, at leastabout 100 J/g, at least about 120 J/g or at least about 150 J/ginclusive off all ranges therebetween.

The quantity of a conductive additive, i.e., the mass or volume fractionof the conductive additive (also referred to herein as the conductiveadditive “loading”) that is used in a given mixture relative to othercomponents, such as an active material, that is suitable for the mixtureto achieve a specified level of bulk electrical conductivity depends onthe cluster state. Percolation theory can be used to select a loading ofconductive additive. Referring now to FIG. 4, a plot of conductivity ofan electrochemical slurry versus conductive additive loading is shown.As the loading of the conductive additive increases, so does theconductivity of the slurry. Three regions of conductivity are depictedon FIG. 4. At low loadings of conductive additive 522, the slurry hasrelatively low conductivity. For example, this slurry with lowconductive additive loading 522 can correspond to the slurry depicted inFIG. 2A-2C, in which there is insufficient conductive material to forman appreciable interparticle network. As the conductive additive loadingincreases, a percolating network 524 begins to form as chains ofconductive additive are able to at least intermittently provideconnectivity between active particles. As the loading increases further(e.g., as shown in the slurry depicted in FIGS. 3A-3C), a relativelystable interparticle networks 530 is formed. The shape and height of thepercolation curve can be modulated by the method of mixing andproperties of the conductive additive, as described herein. The amountof conductive additive used in a slurry, however, can be constrained byother considerations. For example, maximizing battery attributes such asenergy density and specific energy is generally desirable and theloading of active materials directly influences those attributes.Similarly stated, the quantity of other solids, such as active material,must be considered in addition to the loading of conductive material.The composition of the slurry and the mixing process described hereincan be selected to obtain a slurry of relatively uniform composition,while enabling clustering of the conductive additive to improveelectrical conductivity. In other words, the slurry can be formulatedand mixed such that a minimum threshold of conductive additive isincluded to form the interparticle network after an appropriate amountof mixing, thereby maximizing the active material loading. In someembodiments, the amount of conductive additive in the semi-solid cathode140 slurry can be about 0.5-8 vol % by volume, inclusive of all rangestherebetween. In some embodiments, the amount of conductive additive inthe semi-solid anode 150 can be about 0-10 vol %, inclusive of allranges therebetween. In some embodiments, the electronic conductivitiesof the prepared slurries (e.g., the semi-solid cathode 140 slurry or thesemi-solid anode slurry 150) can be at least about 10⁻³ S/cm, or atleast about 10⁻² S/cm, inclusive of all ranges therebetween.

In some embodiments, it is desirable for the electrochemically activeslurry to be “workable,” in order to facilitate material handlingassociated with battery manufacturing. For example, if a slurry is toofluid it can be compositionally unstable. In other words, thehomogeneity can be lost under exposure to certain forces, such asgravity (e.g., solids settling) or centrifugal forces. If the slurry isunstable, solid phase density differences, or other attributes, can giverise to separation and/or compositional gradients. Said another way, ifthe slurry is overly fluidic, which may be the result of low solidsloadings or a significantly disrupted conductive network, the solids maynot be sufficiently bound in place to inhibit particle migration.Alternatively, if an electrochemically active slurry is too solid, theslurry may break up, crumble, and/or otherwise segregate into pieces,which can complicate processing and dimensional control. Formulating theslurry within a band of adequate workability can facilitate easierslurry-based battery manufacturing. Workability of a slurry cantypically be quantified using rheological parameters which can bemeasured using rheometers. Some examples of different types ofrheometers that can be used to quantify slurry workability include:strain or stress-controlled rotational, capillary, slit, andextensional.

In some embodiments, the ratios between active material, conductiveadditive, and electrolyte can affect the stability, workability, and/orrheological properties of the slurry. FIG. 5A-5C depict electrode slurrymixtures with different loadings of active material and conductiveadditive relative to the electrolyte. At a low loading 610 (FIG. 5A),i.e., a slurry in which there is relatively little active material andconductive additive relative to the electrolyte, can result in anunstable or “runny” mixture. As shown, phase separation, i.e.,separation of the active material and conductive additive (solid phase)from the electrolyte (liquid phase), can be observed in the low loading610 mixture. On the contrary, at a high loading mixture 630 (FIG. 5C)where the maximum packing of solid materials in the electrolyte has beenexceeded, the mixture is too dry and is not fluidic enough to beconveyed or processed to a desired shape or thickness. Therefore, asshown in FIG. 5B, there is an optimal loading mixture 620 where theslurry is stable (i.e., the solid particles are maintained insuspension) and is sufficiently fluidic to be workable into electrodes.

In some embodiments, the conductive additive can affect the rheology ofthe suspension. Thus, in such embodiments, at the same loading levels ofconductive additive, increasing concentrations of active materials cancontribute to the rheology of the slurry by increasing the shearviscosity of the suspension. FIG. 6 illustrates rheologicalcharacteristics including the apparent viscosity (η_(appr) Pa·s) andapparent shear rate (γ_(appr) s⁻¹) for various formulations ofsemi-solid cathode 140 slurries that are formulated from about 35% toabout 50% by volume NMC and about 6% to about 12% by volume ofconductive additive C45. FIG. 7 illustrates the rheologicalcharacteristics described herein for various formulations of semi-solidanode 150 slurries formulated from about 35% to about 50% by volumegraphite (PGPT) and about 2% to about 10% by volume of the conductiveadditive C45. The apparent viscosity of the slurries described hereindecreases as the apparent shear rate increases.

The slurry suspensions can be prone to separation and flowinstabilities, structure development, mat formation and/or binderfiltration when flowing under a critical shear stress values due to alow viscosity liquid matrix in the formulation. Such behavior can becharacterized using a capillary rheometer using a small diameter and along L/D. The compositional formulation, especially conductive carbonloading levels, and the extrusion temperature can impact such structuralchanges during a pressure driven flow. FIG. 8 and FIG. 9 illustratetime-pressure graphs for various formulations of a first slurry thatincludes about 35%-50% NMC and about 6%-12% C45 (FIG. 8) and variousformulations of a second slurry that includes about 45%-50% PGPT andabout 2%-6% C45 (FIG. 9). As shown herein, varying amounts of pressureare required to dispense or flow a predefined quantity of slurry withina predetermined time period depending on the rheological characteristicsof the slurry, for example the apparent viscosity and the apparent shearrate. In some embodiments, the apparent viscosity of the prepared slurryat an apparent shear rate of about 1,000 s⁻¹ can be less than about100,000 Pa·s, less than about 10,000 Pa·s, or less than about 1,000Pa·s. In some embodiments, the reciprocal of mean slurry viscosity canbe greater than about 0.001 l/(Pa·s). Some slurry formulations includethree main components such as, for example, active material (e.g., NMC,lithium iron phosphate (LFP), Graphite, etc.), conductive additive(e.g., carbon black), and electrolyte (e.g., a mix of carbonate basedsolvents with dissolved lithium based salt) that are mixed to form theslurry. In some embodiments, the three main components are mixed in abatch mixer. In some embodiments, active materials are first added tothe mixing bowl followed by solvents. In some embodiments, theelectrolyte can be incorporated homogeneously with a dense activematerial without experiencing any ‘backing out’ of material from themixing section of the mixing bowl to form an intermediate material. Oncethe solvent and active materials are fully mixed, they can form a loose,wet paste. The conductive additive can be added to this intermediatematerial (i.e., loose paste), such that it can be evenly incorporatedinto the mix. In some embodiments, the active material can tend not toaggregate into clumps. In other embodiments, the components can becombined using another order of addition, for example, the solvent canbe added first to the mixing bowl, then the active material added, andfinally the additive can be added. In other embodiments, the slurry canbe mixed using any other order of addition.

As mixing energy increases, homogeneity of the mixture can increase. Ifmixing is allowed to continue, eventually excessive mixing energy can beimparted to the slurry. For example, as described herein, excessivemixing energy can produce a slurry characterized by low electronicconductivity. As mixing energy is added to the slurry, the aggregates ofconductive additive can be broken up and dispersed, which can tend toform a network like conductive matrix, as described above with referenceto FIGS. 2 and 3. As mixing continues, this network can degrade ascarbon particles are separated from each other, forming an even morehomogenous dispersion of carbon at the microscopic scale. Such anover-dispersion and loss of network can exhibit itself as a loss ofelectronic conductivity, which is not desirable for an electrochemicallyactive slurry. Furthermore, a slurry having excessive mixing energyimparted to it can display unstable rheology. As the carbon networkaffects mechanical, as well as electronic characteristics of the slurry,formulations which have been over mixed tend to appear “wetter” thanslurries subjected to a lesser amount of mixing energy. Slurries havingexperienced an excessive amount of mixing energy also tend to show poorlong term compositional homogeneity as the solids phases tend to settledue to gravitational forces. Thus, a particular composition can havefavorable electrical and/or rheological properties when subject to anappropriate amount of mixing. For any given formulation, there is arange of optimal mixing energies to give acceptable dispersion,conductivity and rheological stability.

FIGS. 10-12 are plots illustrating an example mixing curve, comparativemixing curves of low and high active material loading for the samecarbon additive loading, and comparative mixing curves of low and highcarbon additive loading for the same active material loading,respectively.

FIG. 10 depicts a mixing curve including the specific mixing energy1110, the speed 1140, and the torque 1170, of slurry, according to anembodiment. The first zone 1173 shows the addition of the raw materials.In some embodiments, the active material is added to the mixer, then theelectrolyte, and finally the conductive additive (carbon black). Thecarbon additive takes the longest time to add to the mixing bowl due tothe difficulty of incorporating a light and fluffy powder into arelatively dry mixture. The torque curve 1170 provides an indication ofthe viscosity, particularly, the change in viscosity. As the viscosityof the mixture increases with the addition of the carbon black, thetorque required to mix the slurry increases. The increasing viscosity isindicative of the mechanical carbon network being formed. As the mixingcontinues in the second zone 1177, the mixing curve shows the dispersionof the raw materials and relatively lower viscosity as evidenced by thedecreased torque required to mix the slurry.

FIG. 11 illustrates the difference between a low and high loading ofactive materials. It can be seen from this curve that the length of timeneeded to add the conductive carbon additive is approximately equal forlow and high active loadings, but the overall torque (and consequentlythe mixing energy) is much higher for the higher active loading. This isindicative of a much higher viscosity.

FIG. 12 illustrates the difference between a low and high conductivecarbon additive loading for the same active material loading. The mixingcurve for the high carbon loading includes the specific mixing energy1310, the speed 1340 and the torque 1373. The first zone 1373 shows theaddition of raw materials. As the viscosity of the mixture increaseswith the addition of the carbon black, the torque required to mix theslurry increases as seen in the first mixing zone 1375. The increasingviscosity is indicative of the carbon network being formed. As themixing continues in the second zone 1377, the mixing curve shows thedispersion of the raw materials and relatively lower viscosity asevidenced by the decreased torque required to mix the slurry. It shouldbe noted that the time needed to add the carbon conductive additive ismuch longer for the high carbon loading and the overall torque (andmixing energy) is also much higher. This mixing curve illustrates thatcarbon loading has a much higher impact on material viscosity thanactive material loading.

As described herein, compositional homogeneity of the slurry willgenerally increase with mixing time and the compositional homogeneitycan be characterized by the mixing index. FIG. 13 illustrates thespecific energy input required to achieve different mixing indexes forslurries of different conductive additive loadings. As shown, a higheramount of specific energy input is required to achieve the desiredspecific index, e.g., about 0.95 as the vol % of conductive additive isincreased in the slurry formulation. In some embodiments, the slurry ismixed until the slurry has a mixing index of at least about 0.8, about0.9, about 0.95, or about 0.975, inclusive of all mixing indicestherebetween.

FIG. 14 illustrates the effect of mixing on certain slurry parametersthat include the mixing index and the electronic conductivity of theslurry, according to an embodiment. The mixing index 1580 risesmonotonically while electronic conductivity 1590 initially increases (asconductive network is dispersed within the media), achieves a maximumvalue, and then decreases (network disruption due to “over mixing”).

In some embodiments, the mixing time can have a simultaneous impact onthe mixing index and conductivity of an electrode slurry. FIG. 15illustrates the effect of mixing time on the mixing index andconductivity of various slurry formulations that include about 45%-50%NMC and about 8% C45. Here, and in subsequently presented measurementsof mixing index, the mixing index is measured by taking sample volumesof 0.12 mm³ from a batch of the electrode slurry that has a total volumegreater than the sum of the individual sample volumes. Each samplevolume of slurry is heated in a thermo gravimetric analyzer (TGA) underflowing oxygen gas according to a time-temperature profile beginningwith a 3 minute hold at room temperature, followed by heating at 20°C./min to 850° C., with the cumulative weight loss between 150° C. and600° C. being used to calculate the mixing index. As shown in FIG. 15,the mixing index is observed to increase but the conductivity isobserved to decrease with increased mixing times. In these embodiments,a mixing time of about 2 minutes provided a good compromise between theconductivity and the mixing index, e.g., the slurry composition composedof 50% NMC and 8% C45 was observed to have a mixing index of about 0.95and a conductivity of about 0.02 S/cm. Any further mixing has a negativeimpact on the conductivity.

FIG. 16 illustrates the effect of mixing time on the mixing index andconductivity of various slurry formulations that include about 45%-50%PGPT and about 2%-4% C45. For the 50% PGPT and 2% C45 mixture, theconductivity is observed to initially rise, peaking at a 4 minute mixingtime, and then decrease by more than a factor of two at 24minutes—consistent with the trend described in FIG. 14. Therefore themixing times required to get an optimal mixing index and conductivity ofa slurry depend on the slurry formulation.

In some embodiments, shear rate can influence mixing dynamics andconductivity. As a result, in some embodiments, the selection of mixingelement rotation speed, container and/or roller size, clearancedimensions/geometry, and so forth can have an effect on conductivity.FIG. 17 is a plot depicting conductivity as a function of mixing timefor two different shear conditions. As shown, the slurry subjected tothe lower shear mixing 2010 is less sensitive to over mixing. The slurrysubject to higher shear mixing 2020 has a slightly higher peakconductivity, reaches the maximum conductivity with less mixing, and ismore sensitive to over mixing. In some embodiments, the optimal mixingtime can be 20 seconds, 2 minutes, 4 minutes or 8 minutes, inclusive ofmixing times therebetween.

In some embodiments, the progression of mixing index over time for afixed RPM (e.g., 100 RPM) mixing speed can depend on the composition ofthe materials being mixed. For example, FIG. 18 illustrates the mixingindex at 100 rpm over time for a first cathode composition that includesabout 45% NMC and about 8% C45, and a second cathode composition thatincludes about 50% NMC and about 8% C45. The mixing index of FIG. 19illustrates the mixing index at 100 rpm over time for a first anodecomposition that includes about 45% PGPT and about 4% C45 and a secondanode composition that includes about 50% PGPT and 2% C45. In each case,nine samples having volumes in the range of about 0.1-0.2 cubicmillimeters were used to quantify the mixing index. As shown in FIG. 18and FIG. 19 the cathode and anode slurries show an increase in themixing index with mixing time. As shown in FIG. 19, the mixing indexcan, for example, plateau after a certain mixing time, e.g., 8 minutes,after which any more mixing does not cause an increase in the mixingindex.

The following examples show the electrochemical properties of variouselectrochemical cells that include the semi-solid electrodes describedherein, compared with two conventional tablet batteries that includeLi-ion Tablet Battery 1 and Li-ion Tablet Battery 2. FIG. 20 summarizesthe electrochemical properties of the semi-solid electrode formulationsand the comparative batteries. These examples are only for illustrativepurposes and are not intended to limit the scope of the presentdisclosure.

Comparative Example 1

A first commercially available tablet battery, Li-ion Tablet Battery 1(also referred to as “Comp Ex 1”) was discharged at various C-rates asshown in FIG. 20. At C/2 rate, corresponding to a current density ofabout 1 mA/cm², the Comp Ex 1 battery had an area specific capacity ofabout 2.7 mAh/cm². At 1 C rate, corresponding to a current density ofabout 2.2 mA/cm², the area specific capacity is still about 2.7 mAh/cm².However, above current density of about 5 mA/cm², the area specificcapacity drops rapidly until it is nearly zero at about 10 mA/cm².

Comparative Example 2

A second commercially available tablet battery, Li-ion Tablet Battery 2(also referred to as “Comp Ex 2”) was discharged at various C-rates asshown in FIG. 20. At C/2 rate, corresponding to a current density ofabout 1.75 mA/cm², the Comp Ex 1 battery had an area specific capacityof about 4.2 mAh/cm². At 1 C rate, corresponding to a current density ofabout 4 mA/cm², the area specific capacity is about 4 mAh/cm². However,above current density of about 4 mA/cm², the area specific capacitydrops rapidly until it is nearly zero at about 7.5 mA/cm².

Example 1

An electrochemical half cell Example 1 (also referred to as “Ex 1”) wasprepared using a semi-solid cathode and a Li metal anode. The LFPsemi-solid cathode was prepared by mixing 45 vol % LFP and 2 vol %carbon black with an ethylene carbonate/dimethyl carbonate/LiPF₆ basedelectrolyte. The cathode slurry was prepared using a batchmixer with aroller mill blade fitting. Mixing was performed at 100 rpm for about 2minutes. The semi-solid slurry had a mixing index greater than 0.9 and aconductivity of 1.5×10⁴ S/cm. The slurry was made into an electrode ofabout 250 μm thickness and was tested against a Li metal anode in aSwagelok cell configuration. The cell was tested using a Maccor batterytester and was cycled between a voltage range of V=2-4.2 V. The cell wascharged using a constant current-constant voltage (CC-CV) procedure witha constant current rate at C/10 and C/8 for the first two cycles then atC/5 for the latter cycles. The constant current charge is followed by aconstant voltage hold at 4.2 V until the charging current decreased toless than C/20. The cell was discharged over a range of currentdensities corresponding to C-rates between C/10 and 5 C. As shown inFIG. 20, at C-rates below C/4, the Ex 1 battery had an area specificcapacity of greater than about 7 mAh/cm², much greater than for thebatteries in Comp Ex 1 and Comp Ex 2. At C/2 rate, corresponding to acurrent density of about 3.7 mA/cm², the Ex 1 battery had an areaspecific capacity of about 6.8 mAh/cm². At 1 C rate, corresponding to acurrent density of about 6 mA/cm², the area specific capacity is about 6mAh/cm². At these C-rates, the area specific capacity is higher than forthe batteries in Comp Ex 1 and Comp Ex 2. Moreover, with increasingcurrent density beyond about 6 mA/cm², the area specific capacity fallsoff much more gradually than for the batteries in Comp Ex 1 and Comp Ex2.

Example 2

An electrochemical half cell Example 2 (also referred to as “Ex 2”) wasprepared using a semi-solid cathode and a lithium metal anode. Thecathode slurry was prepared by mixing 45 vol % Li(Ni,Mn,Co)O₂ and 8 vol% carbon additive with an ethylene carbonate/dimethyl carbonate/LiPF₆based electrolyte. The cathode slurry was prepared using a batchmixerfitted with roller blades. Mixing was performed at 100 rpm for about 4minutes. The slurry was made into an electrode of about 250 μm thicknessand was tested against a Li metal anode in a Swagelok cellconfiguration. The cell was tested using a Maccor battery tester and wascycled over a voltage range of V=2-4.3 V. The cell was charged using aCC-CV procedure with the constant current portion being at C/10 and C/8rate for the first two cycles then at C/5 rate for later cycles. Theconstant current charge step was followed by a constant voltage hold at4.2 V until the charging current decreased to less than C/20. The cellwas then discharged over a range of current density. As shown in FIG.20, at C-rates below C/4, the Ex 2 battery had an area specific capacityof greater than about 10 mAh/cm², much greater than for the batteries inComp Ex 1 and Comp Ex 2. At a C/2 rate, corresponding to a currentdensity of about 4.5 mA/cm², the Ex 2 battery had an area specificcapacity of about 9.5 mAh/cm². At 1 C rate, corresponding to a currentdensity of about 8 mA/cm², the area specific capacity is about 8mAh/cm². At these C-rates, the area specific capacity is higher than forthe batteries in Comp Ex 1 and Comp Ex 2. Moreover, with increasingcurrent density beyond about 6 mA/cm², the areal capacity falls off muchmore gradually than for the batteries in Comp Ex 1 and Comp Ex 2.

Example 3

An electrochemical full cell Example 3 (also referred to as “Ex 3”)included a semi-solid cathode formulated from 35 vol % Li(Ni,Mn,Co)O₂such that the semi-solid cathode had a thickness of about 250 μm, andwas tested against a semi-solid anode formulated from 40 vol % graphiteand 2 vol % carbon additive such that the anode had a thickness of about500 μm. The NMC semi-solid cathode was prepared by mixing 35 vol % NMCand 8 vol % carbon black with an ethylene carbonate/dimethylcarbonate/LiPF₆ based electrolyte. The cathode slurry was prepared usinga batchmixer fitted with roller blades. Mixing was performed at 100 rpmfor 4 minutes. The graphite semi-solid anode was prepared by mixing 40vol % graphite and 2 vol % carbon black using the same electrolyte asthe cathode. The anode slurry formulation was mixed at 100 rpm for about30 seconds to yield a semi-solid anode suspension. The electrodes wereused to form a NMC-Graphite based electrochemical full cell havingactive areas for both cathode and anode of approximately 80 cm². Theelectrochemical full cell Ex 3 was charged using a CC-CV procedure and aconstant current discharge between 2.75-4.2 V using a Maccor tester. Thecell was discharged over a range of current densities. As shown in FIG.20, at C-rates below C/4, the Ex 3 battery had an area specific capacityof about 6 mAh/cm², much greater than for the batteries in Comp Ex 1 andComp Ex 2. At C/2 rate, corresponding to a current density of about 2.8mA/cm², the Ex 3 battery had an area specific capacity of about 5.7mAh/cm². At 1 C rate, corresponding to a current density of about 7.2mA/cm², the area specific capacity is about 7.5 mAh/cm². At theseC-rates, the area specific capacity is higher than for the batteries inComp Ex 1 and Comp Ex 2. Moreover, with increasing current densitybeyond about 6 mA/cm², the area specific capacity falls off much moregradually than for the batteries in Comp Ex 1 and Comp Ex 2.

Example 4

An electrochemical full cell Example 4 (also referred to as “Ex 4”)included a semi-solid cathode formulated from 35 vol % Li(Ni,Mn,Co)O₂such that the semi-solid cathode had a thickness of about 500 μm. Thesemi-solid cathode tested against a semi-solid anode formulated from 40vol % graphite and 2 vol % carbon additive such that the anode had athickness of about 500 μm. The NMC semi-solid cathode was prepared bymixing 35 vol % NMC and 8 vol % carbon additive with an ethylenecarbonate/dimethyl carbonate/LiPF₆ based electrolyte. The cathode slurrywas mixed in a mixer fitted with roller blades for about 4 minutes atabout 100 rpm. The graphite semi-solid anode was prepared by mixing 40vol % graphite and 2 vol % carbon additive using the same electrolyte asthe cathode. The anode slurry formulation was also mixed in a mixerfitted with roller blades for about 30 seconds at 100 rpm. The Ex 4electrochemical full cell had active areas for both cathode and anode ofapproximately 80 cm². The Ex 4 full cell was charged and discharge usinga CC-CV procedure and a constant current discharge between 2.75-4.2 Vusing a Maccor tester. The cell was discharged over a range of currentdensities. As shown in FIG. 20, at C-rates below C/4, the Ex 4 batteryreaches an area specific capacity greater than about 11 mAh/cm², muchgreater than for the batteries in Comp Ex 1 and Comp Ex 2. At C/2 rate,corresponding to a current density of about 4.8 mA/cm², the Ex 4 batteryhad an area specific capacity of about 9.5 mAh/cm². At 1 C rate,corresponding to a current density of about 6.8 mA/cm², the areaspecific capacity is about 7 mAh/cm². At these C-rates, the areaspecific capacity is higher than for the batteries in Comp Ex 1 and CompEx 2. Moreover, with increasing current density beyond 6 mA/cm², thearea specific capacity falls off much more gradually than for thebatteries in Comp Ex 1 and Comp Ex 2.

Example 5

An electrochemical half cell Example 5 (also referred to as “Ex 5”) wasprepared using a semi-solid cathode and a lithium metal anode. Thecathode slurry was prepared by mixing a 55 vol % Li(Ni,Mn,Co)O₂ and 4vol % carbon additive with an ethylene carbonate/dimethylcarbonate/LiPF₆ based electrolyte. The cathode slurry was prepared usinga batch mixer fitted with roller blades. Mixing was performed at 100 rpmfor about 4 minutes. The cathode slurry was formed into an about 250 μmthick semi-solid cathode which was tested against the Li metal anode ina Swagelok cell configuration. The cell was tested using a Maccorbattery tester and was cycled over a voltage range of 2-4.3 V. The cellwas charged using a CC-CV procedure with the constant current portionbeing at C/10 and C/8 rate for the first two cycles than at C/5 rate forlater cycles. The constant current charge step was followed by aconstant voltage hold at 4.2 V until the charging current decreased toless than C/20. The cell was discharged over a range of currentdensities. As shown in FIG. 20, at C-rates below C/4 the Ex 5 batteryhad an area specific capacity of greater than about 9.5 mAh/cm², muchgreater than for the Comp Ex 1 and Comp Ex 2 batteries. At C/2 rate,corresponding to a current density of about 4.5 mA/cm², the Ex 5 batteryhad an area specific capacity of greater than 8 mAh/cm². At 1 C rate,corresponding to a current density of about 7 mA/cm², the area specificcapacity was about 7 mAh/cm². Moreover, with increasing current densitybeyond about 6 mA/cm², the area specific capacity falls of much moregradually than the Comp Ex 1 and the Comp Ex 2 batteries.

Example 6

An electrochemical half cell Example 6 (also referred to as “Ex 6”) wasprepared using a semi-solid cathode and a lithium metal anode. Thecathode slurry was prepared by mixing a 60 vol % Li(Ni,Mn,Co)O₂ and 2vol % carbon additive with an ethylene carbonate/dimethylcarbonate/LiPF₆ based electrolyte. The cathode slurry was prepared usinga batch mixer fitted with roller blades. Mixing was performed at 100 rpmfor about 4 minutes. The cathode slurry was formed into an about 250 μmthick semi-solid which was tested against the Li metal anode in aSwagelok cell configuration. The cell was tested using a Maccor batterytester and was cycled over a voltage range of 2-4.3 V. The Ex 6 cell wascharged using a CC-CV procedure with the constant current portion beingat C/10 and C/8 rate for the first two cycles than at C/5 rate for latercycles. The constant current charge step was followed by a constantvoltage hold at 4.2 V until the charging until the charging currentdecreased to less than C/20. The cell was discharged over a range ofcurrent density. As shown in FIG. 20, at C-rates below C/4 the Ex 6battery had an area specific capacity of greater than about 11.5mAh/cm², much greater than for the Comp Ex 1 and Comp Ex 2 batteries. AtC/2 rate, corresponding to a current density of about 4.5 mA/cm², the Ex6 battery had an area specific capacity of greater than about 9 mAh/cm².At 1 C rate, corresponding to a current density of about 7.5 mA/cm², thearea specific capacity was about 7 mAh/cm². Moreover, with increasingcurrent density beyond about 6 mA/cm², the area specific capacity fallsof much more gradually than the Comp Ex 1 and the Comp Ex 2 batteries.

Example 7

An electrochemical full cell Example 7 (also referred to as “Ex 7”)included a semi-solid cathode formulated from 40 vol % LiFePO₄ such thatthe semi-solid cathode had a thickness of about 500 μm. The semi-solidcathode was tested against a semi-solid anode formulated from 35 vol %graphite and 2 vol % carbon additive such that the anode had a thicknessof about 500 μm. The LFP semi-solid cathode was prepared by mixing 40vol % LFP and 2 vol % carbon additive with an ethylenecarbonate/dimethyl carbonate/LiPF₆ based electrolyte. The cathode slurrywas prepared using a batchmixer fitted with roller blades. Mixing wasperformed at 100 rpm for about 4 minutes. The graphite semi-solid anodewas prepared by mixing 40 vol % graphite and 2 vol % carbon black usingthe same electrolyte as the cathode. The anode slurry formulation wasmixed at 100 rpm for about 30 seconds to yield a semi-solid anodesuspension. The Ex 7 electrochemical cell had active areas for bothcathode and anode of approximately 80 cm². The electrochemical full cellEx 7 was charged using a CC-CV procedure and a constant currentdischarge was performed between 2.0-3.9 V using a Maccor tester. Thecell was discharged over a range of current densities. As shown in FIG.20 at C-rates below C/4, the Ex 7 battery had an area specific capacityof greater than about 9 mAh/cm², much greater than for the batteries inComp Ex 1 and Comp Ex 2. At C/2 rate, corresponding to a current densityof about 4 mA/cm², the Ex 7 battery had an areal capacity of greaterthan about 8 mAh/cm². At 1 C rate, corresponding to a current density ofabout 6 mA/cm², the area specific capacity is about 6 mAh/cm². At theseC-rates, the area specific capacity is higher than for the batteries inComp Ex 1 and Comp Ex 2. Moreover, with increasing current densitybeyond about 6 mA/cm², the area specific capacity falls off much moregradually than for the batteries in Comp Ex 1 and Comp Ex 2.

Example 8

An electrochemical full cell Example 8 (also referred to as “Ex 8”)included a semi-solid cathode formulated from 45 vol % LiFePO₄ such thatthe semi-solid cathode had a thickness of about 330 μm. The semi-solidcathode was tested against a semi-solid anode formulated from 40 vol %graphite and 2 vol % carbon additive such that the anode had a thicknessof about 500 μm. The LFP semi-solid cathode was prepared by mixing 45vol % LFP and 1.9 vol % carbon additive with an ethylenecarbonate/dimethyl carbonate/LiPF₆ based electrolyte. The cathode slurrywas prepared using a batchmixer fitted with roller blades. Mixing wasperformed at 100 rpm for about 25 minutes. The graphite semi-solid anodewas prepared by mixing 40 vol % graphite and 2 vol % carbon black usingthe same electrolyte as the cathode. The anode slurry formulation wasmixed at 100 rpm for about 30 seconds to yield a semi-solid anodesuspension. The Ex 8 electrochemical cell had active areas for bothcathode and anode of approximately 80 cm². The electrochemical full cellEx 8 was charged using a CC-CV procedure. A constant current dischargewas performed between 2.0-3.9 V using a Maccor tester. The cell wasdischarged over a range of current densities. As shown in FIG. 20, atC-rates below C/4, the Ex 8 battery had an area specific capacity ofabout 9 mAh/cm², much greater than for the batteries in Comp Ex. 1 andComp Ex 2.

Example 9

An electrochemical full cell Example 9 (also referred to as “Ex 9”)included a semi-solid cathode formulated from 45 vol % LiFePO₄ such thatthe semi-solid cathode had a thickness of about 470 μm. The semi-solidcathode was tested against a semi-solid anode formulated from 40 vol %graphite and 2 vol % carbon additive such that the anode had a thicknessof about 500 μm. The LFP semi-solid cathode was prepared by mixing 45vol % LFP and 2 vol % carbon additive with an ethylenecarbonate/dimethyl carbonate/LiPF₆ based electrolyte. The cathode slurrywas prepared using a batchmixer fitted with roller blades. Mixing wasperformed at 100 rpm for about 25 minutes. The graphite semi-solid anodewas prepared by mixing 40 vol % graphite and 2 vol % carbon black usingthe same electrolyte as the cathode. The anode slurry formulation wasmixed at 100 rpm for about 30 seconds to yield a semi-solid anodesuspension. The Ex 9 electrochemical cell had active areas for bothcathode and anode of approximately 80 cm². The electrochemical full cellEx 9 was charged using a CC-CV procedure and a constant currentdischarge between 2.0-3.9 V using a Maccor tester. The cell wasdischarged over a range of current densities. As shown in FIG. 20, atC-rates below C/4, the Ex 9 battery had an area specific capacity ofgreater than about 11.5 mAh/cm², much greater than for the batteries inComp Ex 1 and Comp Ex 2.

Example 10

An electrochemical full cell Example 10 (also referred to as “Ex 10”)included a semi-solid cathode formulated from 45 vol % LiFePO₄ such thatthe semi-solid cathode had a thickness of about 500 μm. The semi-solidcathode was tested against a semi-solid anode formulated from 40 vol %graphite and 1.5 vol % carbon additive such that the anode had athickness of about 500 μm. The LFP semi-solid cathode was prepared bymixing 45 vol % LFP and 2 vol % carbon additive with an ethylenecarbonate/dimethyl carbonate/LiPF₆ based electrolyte. The cathode slurrywas prepared using a high speed blade mixer. Mixing was performed forabout 15 seconds until the semi-solid cathode slurry was homogeneous.The graphite semi-solid anode was prepared by mixing 40 vol % graphiteand 1.5 vol % carbon black using the same electrolyte as the cathode.The anode slurry formulation was also mixed in the high speed blademixer for about 15 seconds until homogeneous. The Ex 10 electrochemicalcell had active areas for both cathode and anode of approximately 80cm². The electrochemical full cell Ex 10 was charged using a CC-CVprocedure and a constant current discharge between 2.0-3.9 V using aMaccor tester. The cell was discharged over a range of currentdensities. As shown in FIG. 20, at C-rates below C/4, the Ex 10 batteryhad an area specific capacity of greater than about 11 mAh/cm², muchgreater than for the batteries in Comp Ex 1 and Comp Ex 2.

Example 11

An electrochemical full cell Example 11 (also referred to as “Ex 11”)included a semi-solid cathode formulated from 50 vol % LiFePO₄ such thatthe semi-solid cathode had a thickness of about 454 μm. The semi-solidcathode was tested against a semi-solid anode formulated from 50 vol %graphite and 2 vol % carbon additive such that the anode had a thicknessof about 386 μm. The LFP semi-solid cathode was prepared by mixing 50vol % LFP and 0.8 vol % carbon additive with an ethylenecarbonate/dimethyl carbonate/LiPF6 based electrolyte. The cathode slurrywas prepared using a centrifugal planetary mixer at 1250 rpm for 90seconds. The graphite semi-solid anode was prepared by mixing 50 vol %graphite and 2 vol % carbon black using the same electrolyte as thecathode. The anode slurry formulation was prepared using a centrifugalplanetary mixer at 650 rpm for about 5 minutes. The Ex 11electrochemical cell had active areas for both cathode and anode ofapproximately 80 cm². The electrochemical full cell Ex 11 was chargedusing a CC-CV procedure and a constant current discharge was performedbetween 2.0-3.9 V using a Maccor tester. As shown in FIG. 20 at C-ratesbelow C/4, the Ex 11 battery had an area specific capacity of greaterthan about 10 mAh/cm2, much greater than for the batteries in Comp Ex 1and Comp Ex 2.

Example 12

An electrochemical full cell Example 12 (also referred to as “Ex 12”)included a semi-solid cathode formulated from 60 vol % LiCoO2 such thatthe semi-solid cathode had a thickness of about 408 μm. The semi-solidcathode was tested against a semi-solid anode formulated from 67 vol %graphite and 2 vol % carbon additive such that the anode had a thicknessof about 386 μm. The semi-solid cathode was prepared by mixing 60 vol %LiCoO2 and 0.9 vol % carbon additive with an ethylene carbonate/dimethylcarbonate/LiPF6 based electrolyte. The cathode slurry was prepared usinga centrifugal planetary mixer at 1300 rpm for 90 seconds. The graphitesemi-solid anode was prepared by mixing 67 vol % graphite and 2 vol %carbon black using the same electrolyte as the cathode. The anode slurryformulation was prepared using a centrifugal planetary mixer at 1300 rpmfor about 90 seconds. The Ex 12 electrochemical cell had active areasfor both cathode and anode of approximately 80 cm2. The electrochemicalfull cell Ex 12 was charged using a CC-CV procedure and a constantcurrent discharge was performed between 2.75-4.1 V using a Maccortester. As shown in FIG. 20 at C-rates below C/10, the Ex 12 battery hadan area specific capacity of greater than about 12 mAh/cm2, much greaterthan for the batteries in Comp Ex 1 and Comp Ex 2.

FIG. 20 shows that each of Ex 1 to Ex 12 electrochemical cells have asubstantially superior area specific capacity relative to Comp Ex 1 andComp Ex 2 at C-rates up to about 2 C. Furthermore, at very high C-rates,for example, C-rates greater than 2 C, these electrochemical cells thatinclude semi-solid electrodes still have an area specific capacitysuperior to Comp Ex 1 and Comp Ex 2. For example, above about 10 mA/cm²current density, the area specific capacity of each of Comp Ex 1 andComp Ex 2 is about 0 mAh/cm², which means that no current can be drawnfrom the battery. In contrast, each of the Ex 1 to Ex 12 cells stillretain a substantial portion of the their theoretical area specificcapacity at the 10 mA/cm² current density. Particularly the Ex 4 cellstill had about 5 mAh/cm² charge capacity at the 10 mA/cm² currentdensity corresponding to about 2 C rate, which is about 50% of the areaspecific capacity seen at the C/2 C-rate. Therefore, electrochemicalcells that include semi-solid electrodes described herein can have ahigher area specific capacity than conventional electrochemical cells,and can also be discharged at high C-rates while maintaining asignificant percentage of their area specific capacity.

While various embodiments of the system, methods and devices have beendescribed above, it should be understood that they have been presentedby way of example only, and not limitation. Where methods and stepsdescribed above indicate certain events occurring in certain order,those of ordinary skill in the art having the benefit of this disclosurewould recognize that the ordering of certain steps may be modified andsuch modification are in accordance with the variations of theinvention. Additionally, certain of the steps may be performedconcurrently in a parallel process when possible, as well as performedsequentially as described above. The embodiments have been particularlyshown and described, but it will be understood that various changes inform and details may be made.

The invention claimed is:
 1. An electrochemical cell, comprising: an anode; a semi-solid cathode including a suspension of about 35% to about 75% by volume of an active material and about 0.5% to about 8% by volume of a conductive material in a non-aqueous liquid electrolyte; and an ion-permeable membrane disposed between the anode and the semi-solid cathode, wherein, the semi-solid cathode has a thickness in the range of about 250 μm to about 2,000 μm, and wherein the electrochemical cell has an area specific capacity of at least about 7 mAh/cm² at a C-rate of C/4.
 2. The electrochemical cell of claim 1, wherein the semi-solid cathode has an electronic conductivity of at least about 10⁻³ S/cm.
 3. The electrochemical cell of claim 1, wherein the semi-solid cathode has an area specific capacity of at least about 8 mAh/cm² at a C-rate of C/4.
 4. The electrochemical cell of claim 3, wherein the semi-solid cathode has an area specific capacity of at least about 9 mAh/cm² at a C-rate of C/4.
 5. The electrochemical cell of claim 4, wherein the semi-solid cathode has an area specific capacity of at least about 10 mAh/cm² at a C-rate of C/4.
 6. The electrochemical cell of claim 1, wherein the active material in the semi-solid cathode is about 50% to about 75% by volume.
 7. The electrochemical cell of claim 6, wherein the active material in the semi-solid cathode is about 60% to about 75% by volume.
 8. The electrochemical cell of claim 1, wherein the conductive material in the semi-solid cathode is about 1% to about 6% by volume.
 9. The electrochemical cell of claim 1, wherein the semi-solid cathode suspension has a mixing index of at least about 0.90.
 10. An electrochemical cell, comprising: a semi-solid anode including a suspension of about 35% to about 75% by volume of a first active material and about 0% to about 10% by volume of a first conductive material in a first non-aqueous liquid electrolyte; a semi-solid cathode including a suspension of about 35% to about 75% by volume of a second active material and about 0.5% to about 8% by volume of a second conductive material in a second non-aqueous liquid electrolyte; and an ion-permeable membrane disposed between the semi-solid anode and the semi-solid cathode, wherein, the semi-solid anode and the semi-solid cathode each have a thickness in the range of about 250 μm to about 2,000 μm, and wherein the electrochemical cell has an area specific capacity of at least about 7 mAh/cm² at a C-rate of C/4.
 11. The electrochemical cell of claim 10, wherein the semi-solid cathode has an area specific capacity of at least about 8 mAh/cm² at a C-rate of C/4.
 12. The electrochemical cell of claim 11, wherein the semi-solid cathode has an area specific capacity of at least about 9 mAh/cm² at a C-rate of C/4.
 13. The electrochemical cell of claim 12, wherein the semi-solid cathode has an area specific capacity of at least about 10 mAh/cm² at a C-rate of C/4.
 14. The electrochemical cell of claim 10, wherein the first conductive material in the semi-solid anode is about 0.5% to about 2% by volume.
 15. The electrochemical cell of claim 10, wherein the second active material in the semi-solid cathode is about 50% to about 75% by volume.
 16. An electrochemical cell comprising: an anode; a semi-solid cathode including a suspension of about 35% to about 75% by volume of an active material and about 0.5% to about 8% by volume of a conductive material in a non-aqueous liquid electrolyte; and an ion-permeable membrane disposed between the anode and the semi-solid cathode, wherein, the semi-solid cathode has a thickness in the range of about 250 μm to about 2,000 μm, and wherein the electrochemical cell has an area specific capacity of at least about 7 mAh/cm² at a C-rate of C/2.
 17. The electrochemical cell of claim 16, wherein the semi-solid cathode has an area specific capacity of at least about 8 mAh/cm² at a C-rate of C/2.
 18. The electrochemical cell of claim 17, wherein the semi-solid cathode has an area specific capacity of at least about 9 mAh/cm² at a C-rate of C/2.
 19. The electrochemical cell of claim 18, wherein the semi-solid cathode has an area specific capacity of at least about 10 mAh/cm² at a C-rate of C/2.
 20. The electrochemical cell of claim 16, wherein the semi-solid cathode suspension has a mixing index of at least about 0.90.
 21. An electrochemical cell, comprising: a semi-solid anode including a suspension of about 35% to about 75% by volume of a first active material and about 0% to about 10% by volume of a first conductive material in a first non-aqueous liquid electrolyte; a semi-solid cathode including a suspension of about 35% to about 75% by volume of a second active material and about 0.5% to about 8% by volume of a second conductive material in a second non-aqueous liquid electrolyte; and an ion-permeable membrane disposed between the semi-solid anode and the semi-solid cathode, wherein, the semi-solid anode and the semi-solid cathode each have a thickness in the range of about 250 μm to about 2,000 μm, and wherein the electrochemical cell has an area specific capacity of at least about 7 mAh/cm² at a C-rate of C/2.
 22. The electrochemical cell of claim 21, wherein the electrochemical cell has an area specific capacity of at least about 7 mAh/cm² at a C-rate of C/4.
 23. The electrochemical cell of claim 22, wherein the electrochemical cell has an area specific capacity of at least about 8 mAh/cm² at a C-rate of C/4.
 24. The electrochemical cell of claim 21, wherein the semi-solid anode and the semi-solid cathode each have a thickness in the range of about 250 μm to about 600 μm.
 25. The electrochemical cell of claim 24, wherein the semi-solid anode and the semi-solid cathode each have a thickness in the range of about 300 μm to about 600 μm.
 26. The electrochemical cell of claim 25, wherein the semi-solid anode and the semi-solid cathode each have a thickness in the range of about 350 μm to about 600 μm.
 27. The electrochemical cell of claim 26, wherein the semi-solid anode and the semi-solid cathode each have a thickness in the range of about 400 μm to about 600 μm.
 28. The electrochemical cell of claim 21, wherein the first conductive material in the semi-solid anode is about 0.5% to about 2% by volume.
 29. The electrochemical cell of claim 21, wherein the second active material in the semi-solid cathode is about 50% to about 75% by volume. 